Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever spends the equivalent of a single date from pure earnings, and only what is pure (pure things) ascends to Allah, then Allah certainly accepts it with His right hand, then 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 / 7838