Musnad Abu Ya'la al-Mawsili 160:62

Yahya ibn Ayyub narrated to us, Ismail ibn Ja'far narrated to us, from al-Ala', from his father, from Abu Hurayrah, that the Messenger of Allah (may Allah bless him and grant him peace) said: "When a human dies, his work is cut off from him, except for three: except for an ongoing charity, or knowledge that is benefited from, or a righteous child who supplicates for him."