Musnad Ahmed: Hadith 3859

We were with The Messenger of Allah (ﷺ), and he made one row stand behind him, and there was another row facing the enemy. They all joined the prayer; he said takbeer and they all said takbeer together. Then he led the raw that was behind him in praying one rak'ah, whilst the other row was facing the enemy. Then they went, and the others came, and he led them in praying one rak'ah. Then those whom he had led in praying the second rak'ah stood up and made up (the rak'ah they had not prayed with the Prophet (ﷺ)), then they went back and switched places with the others, and the others came and made up the rak'ah they had missed.