Abu Hurairah (May Allah be pleased with him) reported:
Messenger of Allah (ﷺ) said, "He who gives in charity the value of a date which he legally earned, and Allah accepts only that which is pure, Allah accepts it with His Right Hand and fosters it for him, as one of you fosters his mare, until it becomes like a mountain."[Al- Bukhari and Muslim].
Arabic/English book reference: Book 1, Hadith 561