It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever gives in charity the equivalent of a date from pure earnings, and only what is pure ascends to Allah, then Allah Almighty accepts it with His right hand and nurtures it for its owner, just as one of you nurtures his foal, until it becomes like the mountain of Uhud."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7746