The Messenger of Allah ﷺ said, "Whoever gives in charity the equivalent of a date from lawful earnings, and Allah accepts only what is good, Allah receives it with His right hand and nurtures it for the giver as one of you raises his foal, until it becomes like a mountain."
قال رسول الله ﷺ: من تصدق بعدل تمرة من كسب طيب- ولا يقبل الله إلا الطيب- وإن الله يتقبلها بيمينه ثم يربيها لصاحبه كما يربي أحدكم فلوه حتى تكون مثل الجبل.
Bukhari narrated it in the Book of Zakat (1410), and Muslim in the Book of Zakat (1014), both through the route of Abu Salih, from Abu Hurairah, who related it as mentioned. The wording given is Bukhari's, since Muslim did not present his own wording with this chain, but instead referred back to the text preceding it.His words "from riba" [Rum 30:39] mean that riba outwardly appears to be an increase, but in reality it is something that is effaced, as Allah Most High says, "Allah eliminates riba and causes charity to grow, and Allah does not love any ungrateful sinner" [Baqarah 2:276]. That is, blessing is lifted from wealth gained through riba, because usurious dealings contradict mutual compassion. Economists, after detailed studies, have come to realize that the severe poverty facing mankind is caused by usurious dealings in banks and financial institutions.His words, "And whatever you give in zakat desiring the countenance of Allah, it is those who will receive manifold reward" [Rum 30:39], mean that Allah multiplies the reward of charity given for the sake of Allah. This is confirmed in the sahih hadith.