Authentic Supplication Number 161.

When the Prophet  would finish burying a dead person he would stand over him and say: 'Istaghfiroo li'akheekum wa saloo lahu attathbeeta fa'innahu 'al'ana yus'alu (179).

Footnotes.
(179) Ask forgiveness for your brother, and ask stability for him, for he is now being questioned.

Reporters.
Al-`Adawee said it was comely and that it was reported by Abu Dawood, page 550 of volume 3; Al-Hakim, #370/1, who said it was sound according to the conditions of Al-Bukhari and Muslim; Ath-Thahabi who said it was sound; Al-Bayhaqi, 56/4; and others. Al-Albani said it was sound in his Saheeh Al-Jami` As-Sagheer wa Ziyadatih #4760.