The Messenger of Allah ﷺ said, "The finest act of kindness is for a person to maintain ties with his father's beloved friends after his father has passed away."
حدثنا أحمد بن منيع حدثنا أبو النضر حدثنا الليث بن سعد عن يزيد بن عبد الله بن أسامة بن الهاد عن عبد الله بن دينار
قال رسول الله ﷺ إن أبر البر صلة المرء أهل ود أبيه بعد أن يولي
Muslim reported it in "birr and relations, the chapter on the merit of maintaining ties with the friends of one's father and mother and the like," hadith 2552, from the hadith of Layth bin Saad, transmitted through him, at length.