Sayyiduna Abu Ayyash Zarqi (may Allah be pleased with him) says: We were with the Messenger of Allah (peace and blessings be upon him) at the place of Usfan, when the polytheists confronted us, led by Khalid bin Walid. They were between us and the Qiblah. The Messenger of Allah (peace and blessings be upon him) led us in the Zuhr prayer. They said among themselves: These Muslims are engaged in prayer; if only we could take advantage of their heedlessness. Then they said: Soon, another time for their prayer will come, which is dearer to them than their lives and children. At that very moment, between Zuhr and Asr, Jibreel (peace be upon him) descended with these verses: {وَاِذَا کُنْتَ فِیْہِمْ فَأَقَمْتَ لَہُمُ الصَّلٰوۃَ فَلْتَقُمْ طَائِفَۃٌ مِّنْہُمْ مَّعَکَ وَلْیَأْخُذُوْا اَسْلِحَتَہُمْ فَاِذَا سَجَدُوْا فَلْیَکُوْنُوْا مِنْ وَّرَائِکُمْ وَلْتَأْتِ طَائِفَۃٌ أُخْرٰی لَمْ یُصَلُّوْا فَلْیُصَلُّوْا مَعَکَ} … When you are among them and stand to lead them in prayer, let a group of them stand with you, taking their arms; then when they have prostrated, let them fall to the rear and let another group who have not prayed come forward and pray with you. (An-Nisa: 102) When the time for Asr came, the Messenger of Allah (peace and blessings be upon him) ordered the companions to stand with their weapons. We formed two rows behind him. When the Prophet (peace and blessings be upon him) bowed in ruku', we all bowed, and when he rose from ruku', we also rose. When the Prophet (peace and blessings be upon him) prostrated, only those in the first row behind him prostrated, while those in the second row stood guard. When those who had prostrated stood up, the second row sat down and prostrated in their places. Then (at the beginning of the second rak'ah) the front row moved to the back and the back row came forward. In the same way, all the worshippers bowed in ruku' with the Prophet (peace and blessings be upon him) and rose from ruku'. Then when he prostrated, the first row prostrated with him, and the second row stood guard. When the Prophet and the first row sat after prostration, the second row sat and prostrated (and all sat for tashahhud, then) all together said salam and completed the prayer. The Messenger of Allah (peace and blessings be upon him) led the prayer in this manner twice: once at Usfan and once in the region of Banu Sulaym.