Musnad Ahmad 266:11

Yunus ibn Muhammad narrated to us, he said: Abd al-Rahman ibn al-Ghasil narrated to us, he said: Usayd ibn Ali narrated to me, from his father Ali ibn Ubayd, from Abu Usayd, a companion of the Messenger of Allah (may Allah bless him and grant him peace) who was a Badr-veteran and their freedman, he said: Abu Usayd said: While I was sitting with the Messenger of Allah (may Allah bless him and grant him peace), a man from the Ansar came to him and said: "O Messenger of Allah, is there anything left of the righteousness toward my parents that I should perform for them after their death?" He said: "Yes, four qualities: praying for them, seeking forgiveness for them, fulfilling their pledges, honoring their friend, and maintaining the ties of kinship that you have no kinship with except through them. That is what remains of your righteousness toward them after their death."