“As for the foam, it vanishes as scum; but that which benefits people remains on the earth. Thus does Allah present examples.”
(Qur’an 13:17)
Commentary
He struck a parable for truth and falsehood. He likened disbelief to the foam that rises on the surface of water: it soon disappears, clinging only to the sides of the valleys, and the winds drive it away. Likewise, falsehood fades and vanishes. These two examples were given by Allah to show the firmness of truth and the perishability of falsehood. Falsehood,even if it rises and appears dominant at times, inevitably dissipates, just like foam and impurities.
[Al-Qurṭubī 12/48–51]