Salim bin 'Abdullah bin 'Umar سالم بن عبد الله بن عمر بن الخطاب · The Book of the Fear Prayer

The Messenger of Allah (ﷺ) prayed at Dhi Qarad and the people formed two rows behind him, one row behind him and one row facing the enemy. He led those who were behind him in praying one rak'ah, then they went and took the place of the others, and the others came and he led them in praying one rak'ah, and they did not make it up.

'Abdullah bin 'Abbas said: "The Messenger of Allah (ﷺ) stood and the people stood with him, and he said the takbir and they said the takbir. Then he bowed, and some of them bowed, then he prostrated and they prostrated, then he stood for the second rak'ah and those who had prostrated with him moved back and guarded their brothers, and the other group came and bowed and prostrated with the Prophet (ﷺ). All the people were praying and saying…

The Prophet (ﷺ) offered the fear prayer with those who were behind him, praying two rak'ahs (with them) and two rak'ahs with those who came after them, so the Prophet (ﷺ) prayed four rak'ahs and the others each prayed two rak'ahs.