Muwatta Malik #446

Yahya related to me from Malik from Yazid ibn Ruman from Salih ibn Khawwat from someone who had prayed (the prayer of fear) with the Messenger of Allah, may Allah bless him and grant him peace, on the day of Dhat ar-Riqa that one group had formed a row with him and one group had formed a row opposite the enemy. He then prayed one raka with the group he was with, and then remained standing while they finished by themselves. They then left and formed a row opposite the enemy, and then the other group came and he prayed the remaining raka of his prayer with them, and then remained sitting while they finished by themselves. Then he said the taslim with them.