When you stand (intend) to offer the Salah (the prayer) (Surah Al-Ma’idah 5: 6)

O you who believe! When you stand (intend) to offer the Salah (the prayer), then wash your faces and your hands (forearms) up to the elbows, rub (by passing wet hands over) your heads, and (wash) your feet up to the ankles. If you are in a state of Janaba, purify yourselves (bathe your whole body). But if you are ill or on a journey or any of you comes from the Gha'it (toilet) or you have touched women and you find no water, then perform Tayammum with clean earth and rub therewith your faces and hands. Allah does not want to place you in difficulty, but He wants to purify you, and to complete His Favor to you that you may be thankful.  (Surah Al-Ma’idah 5: 6)

The Order to Perform Wudhu:

Allah said,

When you stand for (intend to offer) the Salah, Allah commanded performing Wudu' for the prayer. This is a command of obligation in the case of impurity, and in the case of purity, it is merely a recommendation. It was said that in the beginning of Islam, Muslims had to perform Wudhu' for every prayer, but later on, this ruling was abrogated. Imam Ahmad bin Hanbal recorded that Sulayman bin Buraydah said that his father said, "The Prophet used to perform Wudhu' before every prayer. On the Day of Victory, he performed Wudhu' and wiped on his Khuffs and prayed the five prayers with one Wudhu'. `Umar (Radhi Allahu Anhu) said to him, `O Messenger of Allah! You did something new that you never did before.' The Prophet (Sallallahu Alayhi wa Sallam) said,

`I did that intentionally O `Umar!'''  

Muslim and the collectors of the Sunan also recorded this Hadith. At-Tirmidhi said,"Hasan Sahih.'' Ibn Jarir recorded that Al-Fadl bin Al-Mubashshir said, "I saw Jabir bin `Abdullah perform several prayers with only one Wudhu'. When he would answer the call of nature, he performed Wudu' and wiped the top of his Khuffs with his wet hand. I said, `O Abu `Abdullah! Do you do this according to your own opinion' He said, `Rather, I saw the Prophet (Sallallahu Alayhi wa Sallam) do the same thing. So, I do what I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam) doing.''' Ibn Majah also recorded this Hadith. Ahmad recorded that `Ubaydullah bin `Abdullah bin `Umar was asked; "Did you see `Abdullah bin `Umar perform Wudhu' for every prayer, whether he was in a state of purity or not,'' So he replied, "Asma' bint Zayd bin Al-Khattab told him that `Abdullah bin Hanzalah bin Abi `Amir Al-Ghasil told her that the Messenger of Allah (Sallallahu Alayhi wa Sallam) was earlier commanded to perform Wudu' for every prayer, whether he needed it or not. When that became hard on him, he was commanded to use Siwak for every prayer, and to perform Wudu' when Hadath (impurity) occurs. `Abdullah (Ibn `Umar) (Radhi Allahu Anhuma)  thought that he was able to do that (perform Wudu' for every prayer) and he kept doing that until he died.'' Abu Dawud also collected this narration. This practice by Ibn `Umar demonstrates that it is encouraged, not obligatory, to perform Wudu' for every prayer, and this is also the opinion of the majority of scholars. Abu Dawud recorded that `Abdullah bin `Abbas (Radhi Allahu Anhuma) said that when the Messenger of Allah (Sallallahu Alayhi wa Sallam) once left the area where he answered the call of nature, he was brought something to eat. They said, "Should we bring you your water for Wudu'' He said,

I was commanded to perform Wudu' when I stand up for prayer. At-Tirmidhi and An-Nasa'i also recorded this Hadith and At-Tirmidhi said, "This Hadith is Hasan.'' Muslim recorded that Ibn `Abbas (Radhi Allahu Anhu) said, "We were with the Prophet (Sallallahu Alayhi wa Sallam) when he went to answer the call of nature and when he came back, he was brought some food. He was asked, `O Messenger of Allah! Do you want to perform Wudu'' He said,

`Why am I about to pray so that I have to make Wudhu'.'''

The Intention and Mentioning Allah's Name for Wudhu

Allah said;

then wash your faces...  The obligation for the intention before Wudu' is proven by this Ayah;

When you stand (intend) to offer the Salah then wash your faces...  This is because it is just like the Arabs saying; "When you see the leader, then stand.'' Meaning stand for him. And the Two Sahihs recorded the Hadith,

Actions are judged by their intentions, and each person will earn what he intended. It is also recommended before washing the face that one mentions Allah's Name for the Wudu'. A Hadith that was narrated by several Companions states that the Prophet (Sallallahu Alayhi wa Sallam) said,

There is no Wudu' for he who does not mention Allah's Name over it. It is also recommended that one washes his hands before he puts his hands in the vessel of water, especially after one wakes up from sleep, for the Two Sahihs recorded that Abu Hurayrah (Radhi Allahu Anhu) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said,

If one of you wakes up from his sleep, let him not put his hand in the pot until he washes it thrice, for one of you does not know where his hand spent the night.  The face according to the scholars of Fiqh starts where the hair line on the head starts, regardless of one's lack or abundance of hair, until the end of the cheeks and chin, and from ear to ear.

Passing the Fingers through the Beard While Performing Wudhu

Imam Ahmad recorded that Abu Wa'il said, "I saw `Uthman (Radhi Allahu Anhu) when he was performing Wudu'... When he washed his face, he passed his fingers through his beard three times. He said, `I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam) do what you saw me doing.''' At-Tirmidhi and Ibn Majah also recorded this Hadith. At-Tirmidhi said "Hasan Sahih.'' while Al-Bukhari graded it Hasan.
How to Perform Wudhu

Imam Ahmad recorded that Ibn `Abbas (Radhi Allahu Anhuma) once performed Wudu' and took a handful of water and rinsed his mouth and nose with it. He took another handful of water and joined both hands and washed his face. He took another handful of water and washed his right hand, and another handful and washed his left hand with it. He next wiped his head. Next, he took a handful of water and sprinkled it on his right foot and washed it and took another handful of water and washed his left foot. When he finished, he said, "This is how I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam) (performing Wudu').'' Al-Bukhari also recorded it. Allah said,

and your hands (forearms) up to (Ila) the elbows... meaning, including the elbows. Allah said in another Ayah [using Ila],

And devour not their substance to (Ila) your substance (by adding or including it in your property). Surely, this is a great sin. (Surah An-Nisa' 4: 2)  It is recommended that those who perform Wudu' should wash a part of the upper arm with the elbow. Al-Bukhari and Muslim recorded that Abu Hurayrah (Radhi Allahu Anhu) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said,

On the Day of Resurrection, my Ummah will be called "those with the radiant appendages'' because of the traces of Wudu'. Therefore, whoever can increase the area of his radiance should do so. Muslim recorded that Abu Hurayrah (Radhi Allahu Anhu) said, "I heard my intimate friend (the Messenger (Sallallahu Alayhi wa Sallam)) saying,

The radiance of the believer reaches the areas that the water of (his) Wudu' reaches.''  Allah said next,

Rub your heads.  It is recorded in the Two Sahihs that Malik bin `Amr bin Yahya Al-Mazini said that his father said that a man said to `Abdullah bin Zayd bin `Asim, the grandfather of `Amr bin Yahya and one of the Companions of the Messenger , "Can you show me how the Messenger of Allah (Sallallahu Alayhi wa Sallam) used to perform Wudu''' `Abdullah bin Zayd said, "Yes.'' He then asked for a pot of water. He poured from it on his hands and washed them twice, then he rinsed his mouth and washed his nose [with water] thrice [by putting water in it and blowing it out]. He washed his face thrice and after that he washed his forearms up to the elbows twice. He then passed his wet hands over his head from its front to its back and vice versa, beginning from the front and taking them to the back of his head up to the nape of the neck and then brought them to the front again from where he had started. He next washed his feet.

A similar description of the Wudu' of the Messenger of Allah (Sallallahu Alayhi wa Sallam) was performed by `Ali in the Hadith by `Abdu Khayr. Abu Dawud recorded that Mu`awiyah and Al-Miqdad bin Ma`dikarib narrated similar descriptions of the Wudu' of the Messenger of Allah . These Hadiths indicate that it is necessary to wipe the entire head. `Abdur-Razzaq recorded that Humran bin Aban said, "I saw `Uthman bin `Affan (Radhi Allahu Anhu) performing Wudu', and he poured water over his hands and washed them thrice, and then rinsed his mouth and washed his nose [by putting water in it, and then blowing it out]. Then he washed his face thrice, and then his right forearm up to the elbows thrice, and washed the left forearm thrice. Then he passed his wet hands over his head, then he washed his right foot thrice, and next his left foot thrice. After that `Uthman (Radhi Allahu Anhu) said, `I saw the Prophet (Sallallahu Alayhi wa Sallam) performing Wudu' like this, and said,

If anyone performs Wudu' like that of mine and offers a two-Rak`ah prayer during which he does not think of anything else, then his past sins will be forgiven.''' Al-Bukhari and Muslim also recorded this Hadith in the Two Sahihs. In his Sunan, Abu Dawud also recorded it from `Uthman (Radhi Allahu Anhu), under the description of Wudu', and in it, that he wiped his head one time.

The Necessity of Washing the Feet

Allah said,

and your feet up to ankles  Ibn Abi Hatim recorded that Ibn `Abbas (Radhi Allahu Anhu) stated that the Ayah refers to washing (the feet). `Abdullah bin Mas`ud, `Urwah, `Ata', `Ikrimah, Al-Hasan, Mujahid, Ibrahim, Ad-Dahhak, As-Suddi, Muqatil bin Hayyan, Az-Zuhri and Ibrahim At-Taymi said similarly. This clearly indicates the necessity of washing the feet, just as the Salaf have said, and not only wiping over the top of the bare foot.

The Hadiths that Indicate the Necessity of Washing the Feet

We mentioned the Hadiths by the two Leaders of the Faithful, `Uthman and `Ali, and also by Ibn `Abbas, Mu`awiyah, `Abdullah bin Zayd bin `Asim and Al-Miqdad bin Ma`dikarib, (Radhi Allahu Anhum) that the Messenger of Allah (Sallallahu Alayhi wa Sallam) washed his feet for Wudu', either once, twice or thrice. It is recorded in the Two Sahihs that `Abdullah bin `Amr (Radhi Allahu Anhu) said, "The Messenger of Allah (Sallallahu Alayhi wa Sallam) was once late during a trip we were taking, and he caught up with us when the time remaining for the `Asr prayer was short. We were still performing Wudu' (in a rush) and we were wiping our feet. He shouted at the top of his voice,

Perform Wudu' thoroughly. Save your heels from the Fire.'' The same narration was also collected in the Two Sahihs from Abu Hurayrah. Muslim recorded that `A'ishah (Radhi Allahu Anha) said that the Prophet (Sallallahu Alayhi wa Sallam) said,

Perform Wudu' thoroughly. Save your heels from the Fire. `Abdullah bin Al-Harith bin Jaz' said that he heard the Messenger of Allah (Sallallahu Alayhi wa Sallam) saying,

Save your heels and the bottom of the feet from the Fire.  It was recorded by Al-Bayhaqi and Al-Hakim, and this chain is Sahih. Muslim recorded that `Umar bin Al-Khattab (Radhi Allahu Anhu) said that a man once performed Wudu' and left a dry spot the size of a fingernail on his foot. The Prophet (Sallallahu Alayhi wa Sallam) saw that and he said to him,

Go back and perform proper Wudu'.  Al-Hafiz Abu Bakr Al-Bayhaqi also recorded that Anas bin Malik (Radhi Allahu Anhu) said that a man came to the Prophet (Sallallahu Alayhi wa Sallam), after he performed Wudu' and left a dry spot the size of a fingernail on his foot. The
Messenger of Allah (Sallallahu Alayhi wa Sallam) said to him,

Go back and perform proper Wudu'.  Imam Ahmad recorded that some of the wives of the Prophet (Sallallahu Alayhi wa Sallam) said that the Prophet (Sallallahu Alayhi wa Sallam) saw a man praying, but noticed a dry spot on his foot, the size of a Dirham. The Messenger of Allah (Sallallahu Alayhi wa Sallam) ordered that man to perform Wudu' again. This Hadith was also collected by Abu Dawud from Baqiyyah, who added in his narration, "And (the Prophet (Sallallahu Alayhi wa Sallam) ordered him) to repeat the prayer.'' This Hadith has a strong, reasonably good chain of narrators. Allah knows best.

The Necessity of Washing Between the Fingers

In the Hadith that Humran narrated, `Uthman (Radhi Allahu Anhu) washed between his fingers when he was describing the Wudu' of the Prophet (Sallallahu Alayhi wa Sallam). The collectors of the Sunan recorded that Laqit bin Sabrah said, "I said, `O Messenger of Allah! Tell me about Wudu'.' The Messenger replied,

Perform Wudu' thoroughly, wash between the fingers and exaggerate in rinsing your nose, unless you are fasting.”

Wiping Over the Khuffs is an Established Sunnah

Imam Ahmad bin Hanbal recorded that Aws bin Abi Aws (Radhi Allahu Anhu) said, "I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam) perform Wudu' and wipe over his Khuffs. He then stood up for prayer.'' Abu Dawud recorded this Hadith by Aws bin Abi Aws (Radhi Allahu Anhu), who said in this narration, "I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam), after he answered the call of nature, perform Wudu' and wipe over his Khuffs and feet.'' Imam Ahmad recorded that Jarir bin `Abdullah Al-Bajali said, "I embraced Islam after Surat Al-Ma'idah was revealed and I saw the Messenger of Allah  (Sallallahu Alayhi wa Sallam) wipe after I became Muslim.'' It is recorded in the Two Sahihs that Hammam said, "Jarir answered the call of nature and then performed Wudu' and wiped over his Khuffs. He was asked, `Do you do this' He said, `Yes. I saw the Messenger of Allah (Sallallahu Alayhi wa Sallam), after he answered the call of nature, perform Wudu' and wipe on his Khuffs.''' Al-A`mash commented that Ibrahim said, "They liked this Hadith because Jarir embraced Islam after Surat Al-Ma'idah was revealed.'' This is the wording collected by Muslim. The subject of the Messenger of Allah (Sallallahu Alayhi wa Sallam) wiping over his Khuffs, instead of washing the feet, if he had worn his Khuffs while having Wudu', reaches the Mutawatir grade of narration, and they describe this practice by his words and actions.

Performing Tayammum with Clean earth When There is no Water and When One is Ill

Allah said,

But if you are ill or on a journey or any of you comes from the Gha'it (toilet), or you have touched women and you find no water, then perform Tayammum with clean earth and rub therewith your faces and hands.   We discussed all of this in Surat An-Nisa', and thus we do not need to repeat it here. We also mentioned the reason behind revealing this Ayah. Yet, Al-Bukhari mentioned an honorable Hadith here specifically about the Tafsir of this noble Ayah. He recorded that `A'ishah (Radhi Allahu Anha) said, "Upon returning to Al-Madinah, a necklace of mine was broken (and lost) in Al-Bayda' area. Allah's Messenger stayed there and went to sleep with his head on my lap. Abu Bakr (`A'ishah's father) came and hit me on my flank with his hand saying, `You have detained the people because of a necklace' So I wished I were dead because (I could not move) the Messenger (Sallallahu Alayhi wa Sallam) was sleeping on my lap and because of the pain Abu Bakr caused me. Allah's Messenger (Sallallahu Alayhi wa Sallam) got up when dawn broke and there was no water. So Allah revealed,

O you who believe! When you stand (intend) to offer As-Salah (the prayer), then wash your faces until the end of the Ayah. Usayd bin Al-Hudayr said, `O the family of Abu Bakr! Allah has blessed the people because of you. Therefore, you are only a blessing for the people.'' Allah said,

Allah does not want to place you in difficulty,  This is why He made things easy and lenient for you. This is why He allowed you to use Tayammum when you are ill and when you do not find water, to make things comfortable for you and as mercy for you. Allah made Tayammum in place of Wudu', and Allah made it the same as ablution with water for the one who it is legitimate for, except for certain things, as we mentioned before. For example; Tayammum only involves one strike with the hand on the sand and wiping the face and hands. Allah said,

but He wants to purify you, and to complete His favor on you that you may be thankful,  for His bounties on you, such as His easy, kind, merciful, comfortable and lenient legislation.

Supplicating to Allah after Wudhu

The Sunnah encourages supplicating to Allah after Wudu' and states that those who do so are among those who seek to purify themselves, as the Ayah above states. Imam Ahmad, Muslim and the collectors of Sunan narrated that `Uqbah bin `Amir said, "We were on watch, guarding camels, and when my turn to guard came, I took the camels back at night. I found that the Messenger of Allah (Sallallahu Alayhi wa Sallam)  was giving a speech to the people. I heard these words from that speech:

Any Muslim who performs Wudu' properly, then stands up and prays a two Rak'ah prayer with full attention in his heart and face, will earn Paradise. I said, `What a good statement this is!' A person who was close by said, `The statement he said before it is even better.' When I looked, I found that it was `Umar (Radhi Allahu Anhu), who said, `I saw that you just came. The Prophet (Sallallahu Alayhi wa Sallam) said,

When any of you performs Wudu' properly and says, `I bear witness that there is no deity worthy of worship except Allah and that Muhammad is His servant and Messenger', the eight doors of Paradise will be opened for him so that he can enter from any door he wishes.''  This is the wording collected by Muslim.

The Virtue of Wudhu

Malik recorded that Abu Hurayrah (Radhi Allahu Anhu) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said,

When the Muslim or the believing servant performs Wudu' and washes his face, every sin that he looked at with his eyes will depart from his face with the water, or with the last drop of water. When he washes his hands, every sin that his hands committed will depart from his hands with the water, or with the last drop of water. When he washes his feet, every sin to which his feet took him will depart with the water, or with the last drop of water. Until, he ends up sinless. Muslim also recorded it. Muslim recorded that Abu Malik Al-Ash`ari (Radhi Allahu Anhu) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said,

Purity is half of faith and Alhamdulillah (all the thanks are due to Allah) fills the Mizan (the Scale). And Subhan Allah and Allahu Akbar (all praise is due to Allah, and Allah is the Most Great) fills what is between the heaven and earth. As-Sawm (the fast) is a Junnah (a shield), Sabr (patience) is a light, Sadaqah (charity) is evidence (of faith) and the Qur'an is proof for, or against you. Every person goes out in the morning and ends up selling himself, he either frees his soul or destroys it. Muslim recorded that Ibn `Umar (Radhi Allahu Anhuma) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said,

Allah does not accept charity from one who commits Ghulul, or prayer without purity.

Source: Tafsir ibn Kathir (Abridged)

Note: Ghulul means to behave treacherously. Here is about stealing from the goods taken during war.