Musnad Abu Ya'la al-Mawsili 139:27

Abu Bakr ibn Abi Shaybah narrated to us, 'Abdah ibn Sulayman narrated to us, from Sufyan, from Sulayman al-Taymi, who said: I heard Anas ibn Malik saying: The Messenger of Allah (may Allah bless him and grant him peace) said: "I passed by Musa while he was praying in his grave."