Musnad Ahmad 10:19

'Affan narrated to us, Abu 'Awanah narrated to us, from 'Umar ibn Abi Salamah, from his father, who said: The storyteller of the people of Palestine narrated to me, saying: I heard 'Abd al-Rahman ibn 'Awf saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Three things—by the One in whose hand is the soul of Muhammad—I would certainly swear to them: Wealth does not decrease from charity, so give charity. And no servant pardons an injustice, seeking thereby the Face of Allah, but that Allah raises him in honor by it." And Abu Sa'id, the freed slave of Banu Hashim, said: "But that Allah increases him in honor by it on the Day of Resurrection." "And no servant opens a door of begging but that Allah opens upon him a door of poverty."