Musnad Abu Ya'la al-Mawsili 4:36

Abu Bakr ibn Abi Shaybah narrated to us, Abu al-Ahwas narrated to us, from Simak, from Musa ibn Talhah, from his father, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you prays, let him place in front of him something like the back of a saddle, then let him pray, and let him not be concerned about whoever passes beyond that."