Hadith 6:1132
Hushaym and Hafs narrated to us, from al-Shaybani, from al-Sha'bi, from Ibn Abbas, who said: The Prophet (peace and blessings of Allah be upon him) prayed over a grave after it had been buried.
حدثنا هشيم وحفص عن الشيباني عن الشعبي عن بن عباس قال صلى النبي صلى الله عليه وسلم على قبر بعد ما دفن