Abu Dawud Book 36, Hadith Number 5123.

Narated By AbuUsayd Malik ibn Rabi’ah as-Sa’idi : While we were with the Apostle of Allah! (PBUH) a man of Banu Salmah came to Him and said: Apostle of Allah is there any kindness left that I can do to my parents after their death? He replied: Yes, you can invoke blessings on them, forgiveness for them, carry out their final instructions after their death, join ties of relationship which are dependent on them, and honour their friends.