Sayyiduna Abu Ayyash Zurqi رضي الله عنه said:“We were with the Messenger of Allah صلى الله عليه وسلم at Usfan, and on the side of the polytheists was Khalid bin Walid. We performed the Zuhr prayer, so the polytheists said: ‘We have found an opportunity of negligence; if only we had attacked.’ Then the verse of shortening (qasr) was revealed. At the time of Asr, the Messenger of Allah صلى الله عليه وسلم divided the companions into two rows. One row performed bowing and prostration with him, while the other row kept guard. Then they switched, and the other row performed prostration. Then the prayer was completed in this manner.”