Musnad Ahmad 701:3

Abdullah ibn Muhammad ibn Abi Shaybah narrated to us—Abdullah said: And I heard it myself from Abdullah ibn Muhammad ibn Abi Shaybah—Abd al-Aziz ibn Muhammad al-Darawardi narrated to us, from Isma'il ibn Abi Habibah, from Abdullah ibn Abd al-Rahman, who said: "The Prophet, may Allah bless him and grant him peace, came to us and led us in prayer in the mosque of Banu Abd al-Ashhal. I saw him placing his hand inside his garment when he prostrated."