Maliks Muwatta Book 58, Hadith Number 1.

Malik related to me from Yahya ibn Said from Abu’l-Hubab Said ibn Yasar that the Messenger of Allah, may Allah bless him and grant him peace, said, “Whoever gives sadaqa from good earning – and Allah only accepts the good – it is as if he placed it in the palm of the Merciful to raise it, as one of you raises his foal or young camel until it is like the mountain.”