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 a single date in charity from pure earnings, Allah Almighty accepts it with His right hand and keeps nurturing it, just as one of you nurtures his foal, until it becomes like a mountain or even greater."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7839