Musnad Ahmad 30:3848

Ahmad Abu Salih narrated to us, Muhammad bin Muslim—meaning Ibn Abi al-Waddah Abu Sa’id al-Mu’addib—narrated to us—in Dhu al-Qi’dah of the year seventy, and he mentioned a hadith—and he mentioned this from Muhammad bin ‘Amr bin ‘Alqamah, from Abu Salamah, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "Indeed, when a man gives in charity a date from what is pure—and Allah does not accept except what is pure—it falls into the hand of Allah, so He nurtures it for him just as one of you nurtures his foal or his young camel, until it becomes in His hand like the mountain."