Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) said: "Whoever among the Muslims gives charity from pure earnings—and Allah Almighty accepts only that which is pure—then Allah Almighty takes (that charity) in His Hand of Power and begins to nurture it, just as a person raises his young animal, until a single date becomes as large as the mountain of Uhud."
Hadith Referenceصحیح ابن حبان / كتاب الزكاة / 3316
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «الروض النضير» (1083)، «ظلال الجنة» (623): م.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط الشيخين