Musannaf Ibn Abi Shayba 3:474

Abu Khalid al-Ahmar narrated to us, from Hajjaj, from Abu Ishaq, from al-Muhallab ibn Abi Sufrah, from a man among the companions of the Prophet, may Allah bless him and grant him peace, who said: The Prophet, may Allah bless him and grant him peace, said: "If there is between you and the one who passes in front of you [a distance] like the back of a saddle, then it has screened you."