The Prophet's (Sallallahu ‘Alayhi wa Sallam) Guidance regarding Voluntary Charity (Sadaqah At-Tatawwu')
Excerpt from the Book: Provisions for the Hereafter
by Ibn Qayyim
was the greatest of the people in giving charity with whatever was in his hands and he did not overestimate the value of anything which Allah gave him, nor did he underestimate it (i.e. nothing in his possession was considered to much or too little by him to be given in charity). If anyone asked hirn for something, he would give it to him, whether it was little or much and his happiness and joy in giving were greater than that of the receiver. And when a person in need submitted his case to him, he would give preference to his needs over his own, sometimes with his food and sometimes with his clothes.
giving and charity were of different types: Sometimes, it took the form of a gift, sometimes charity and sometimes a grant; and sometimes, he would buy something and then give it to the seller along with its price. At other.times, he would borrow something and then return, more than he had borrowed. He would accept a gift and in return, he would give something of greater value,  out of kindness and in order to express all diverse forms of charitable deeds to the utmost of his ability. His benevolence was expressed with his property, his actions and his words. He would give whatever he had, he would order the giving of charity and he would encourage it, so that if a miserly person saw him, his behaviour would call upon him to be. giving.
Anyone who associated with him
could not help but be kind and generous. For this reason, he was the most open-hearted of people and the finest soul among them; for charity and righteou deeds, have an amazing ability to open the heart and this was in addition to the things by which Allah had distinguished him, such as His opening his heart by the Message, its special characteristics and its consequences and the opening of his heart to compassion and the removal of Satan's portion (i.e. influence) from it.
And the greatest cause of open-heartedness is monotheism,Ttawheed; and in accordance with its completeness, its strength and its increase, a person's heart will be opened; Allah, Most High says:"Is he whose breast Allah has opened to Islam, so that he is in light from his Lord (as he who is a non-Muslim)?" 
"And whomsoever Allah wills to guide, He opens his breast to Islam; and whomsoever He wills to send astray, He makes his breast closed and constricted."
Another cause is the Light which Allah places in the heart, and that is the Light of Faith (Iman). It is reported in 'Sunan At-Tirmidhi' in a Marfu' form:"When the Light enters the heart, it is expanded and opened." 
Another cause is knowledge, for it opens the heart and expands it; but this is not true for all knowledge- only for that which we have inherited from the Prophet
Still another cause is turning in repentance to Allah and loving Him with all one's heart. And love has an amazing effect in opening the heart and in bringing about goodness of the soul. And the more love for Him grows stronger, the more the heart is opened and it is not straitened except by the idle ones.
And another cause is being constant in remembrance of Allah, for Dhikr has an amazing effect in opening the heart.
Also among them is acting righteously (Ihsan) towards all created beings and benefitting them to the best of one's ability, through one's wealth and status and by physically helping them with all sorts of righteous deeds.
As for spiritual happiness and bliss, it is forbidden to every coward, as it is forbidden to every miser and every person who turns away from Allah, unmindful of remembrance of Him and ignorant of Him and His Religion and whose heart is attached to other than Him; and no heed should be paid to the opening of the heart of such a person due to something which befalls him, nor to the anguish of his heart caused by some mishap befalling him for verily, the things which affect the heart are removed by removing their causes (i.e. if happiness is dependent on some material thing, then the removal of that material thing will cause unhappiness); what is relied upon is the quality of the heart that makes it open or straitened for it is the measure of the heart.
Another cause - indeed, the greatest of them - is the removal of corruption in the heart caused by reprehensible characteristics.
And also among them is abandoning looking into undesirable things, vain speech, listening to undesirable things, mixing with undesirable people, eating bad things and sleeping excessively.
 Narrated by Al-Bukhari
 Surah Az-Zumar 39:22
 Surah Al-An'am 6:125
 According to Shu'aib and 'Abdul Qadir Al-Arna'ut, who checked the Ahadeeth of the full version of 'Zad Al-Ma'ad', it was not narrated by At-Tirmidhi, as Ibn Al-Qayyim states, but by At-Tabari, on the authority of Ibn Mas'ood
and it was mentioned by As-Suyuti in 'Ad-Darr Al-Manthur' and by Ibn Katheer, who related it from Ibn Abi Hatim and Ibn Jareer (At-Tabari). Some of its chains of narrators are connected (Muttasil) and some of them are broken (Mursal) and they all strengthen each other.Pages 113-114