Musnad Ahmad 25:1645

Rawh narrated to us, Zakariya narrated to us, ‘Amr ibn Dinar informed us, from ‘Ikrimah, from Ibn ‘Abbas, that a man said: "O Messenger of Allah, my mother has passed away; will it benefit her if I give charity on her behalf?" He said: "Yes." He said: "I have a garden of date palms, and I call you to witness that I have given it as charity on her behalf."