Two Parables proving that Truth remains and Falsehood perishes
As-Salamu-Alaikum wa Rahmatullahi wa Barakatuhu
This honorable Ayah contains two parables which affirm that truth remains and increases, while falsehood diminishes and perishes. Allah said, He sends down water from the sky,
He sends rain, and the valleys flow according to their measure,
each valley taking its share according to its capacity, for some valleys are wider and can retain more water than others which are small and thus retain smaller measures of water. This Ayah indicates that hearts differ, for some of them can retain substantial knowledge while others cannot entertain knowledge, but rather are bothered by knowledge, but the flood bears away the foam that mounts up to the surface
of the water that ran down the valleys; this is the first parable. Allah said next, and (also) from that (ore) which they heat in the fire in order to make ornaments or utensils...
This is the second parable, whereas gold and silver ore is heated with fire to make adornments with it, and iron and copper ore are heated to make pots and the like with it. Foam also rises to the surface of these ores, just as in the case with water, thus does Allah (by parables) show forth truth and falsehood,
when they both exist, falsehood does not remain, just as foam does not remain with the water or the gold and silver ores which are heated in fire. Rather, foam dissipates and vanishes, Then, as for the foam it passes away as scum upon the banks,
for it carries no benefit and dissipates and scatters on the banks of the valley. The foam also sticks to trees or is dissipated by wind, just as the case with the scum that rises on the surface of gold, silver, iron and copper ores; it all goes away and never returns. However, water, gold and silver remain and are used to man's benefit. This is why Allah said next, while that which is for the good of mankind remains in the earth. Thus Allah sets forth parables.
Allah said in a similar Ayah, And these similitudes We put forward for mankind; but none will understand them except those who have knowledge.) [Surah Al-‘Ankabut 29]
Some of the Salaf (rightly guided ancestors) said, "When I would read a parable in the Qur'an that I could not comprehend, I would cry for myself because Allah the Exalted says, But none will understand them except those who have knowledge.'' [Surah Al-‘Ankabut 29]
Ali bin Abi Talhah reported that Abdullah bin Abbas (Radhi Allahu Anhuma) commented on Allah's statement, He sends down water from the sky, and the valleys flow according to their measure,)
"This is a parable that Allah has set; the hearts carry knowledge from Him, and certainty according to the amount of doubt. As for doubt, working good deeds does not benefit while it exists. As for certainty, Allah benefits its people by it, hence Allah's statement, Then, as for the foam,
which refers to doubt, it passes away as scum upon the banks, while that which is for the good of mankind remains in the earth,
in reference to certainty. And just as when jewelry is heated in fire and is rid of its impurity, which remains in the fire, similarly Allah accepts certainty and discards doubt.''The Qur'an and the Sunnah contain Parables that use Water and Fire
Allah has set two examples in the beginning of Surah Al-Baqarah (chapter 2) about the hypocrites, one using fire and another using water. Allah said, Their likeness is as the likeness of one who kindled a fire; then, when it illuminated all around him. [Surah Al-Baqarah 2]
then He said, Or like a rainstorm in the sky, bringing darkness, thunder, and lightning. [Surah Al-Baqarah 2]
Allah also has set two parables for the disbelievers in Surah An-Nur (chapter 24), one of them is, As for those who disbelieved, their deeds are like a mirage in a desert.[Surah An-Nur 24: 39]
The mirage occurs during intense heat. It is recorded in the Two Sahihs that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said, It will be said to the Jews on the Day of Resurrection, "What do you desire'' They will reply, "We need to drink, for we have become thirsty, O our Lord!'' It will be said, "Will you then proceed to drink,'' and they will head towards the Fire, which will appear as a mirage, its various parts consuming the other parts.''
Allah said in the second parable (in Surah An-Nur); Or is like the darkness in a vast deep sea.[Surah An-Nur 24]
In the Two Sahihs it is recorded that Abu Musa Al-Ash’ari (Radhi Allahu Anhu) said that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said, The example of guidance and knowledge with which Allah has sent me is like abundant rain falling on the earth, some of which was fertile soil that absorbed the rain water and brought forth vegetation and grass in abundance. And another portion of it was hard, it held the rain water and Allah benefited the people with it and they utilized it for drinking, grazing, making their animals drink from it and for irrigation purposes. And another portion of it fell on barren land, which could neither hold the water nor bring forth vegetation. The first is the example of the person who comprehends Allah's religion and gets benefit, as well as benefiting others (from the knowledge and guidance) which Allah has revealed through me and learns and then teaches others. The last example is that of a person who does not care for it and does not embrace Allah's guidance revealed through me.
This parable uses water in it.
In another Hadith that Imam Ahmad collected, Abu Hurayrah (Radhi Allahu Anhu) narrated that the Messenger of Allah (Sallallahu Alayhi wa Sallam) said, My example and the example of you is like that of a person who lit a fire. When the fire illuminated his surroundings, butterflies and insects started falling into it, as they usually do, and he started swatting at them to prevent them from falling; but they overwhelmed him and kept falling into the fire. This is the parable of me and you, I am holding you by the waist trying to save you from the Fire, saying, "Go away from the Fire,'' yet you overwhelm me and fall into it.
The Two Sahihs also collected this Hadith. This is a parable using fire.
Reference: Tafsir ibn Kathir (abridged) English version.