Muwatta Malik #447

Yahya related to me from Malik from Yahya ibn Said from al-Qasim ibn Muhammad from Salih ibn Khawwat that Sahl ibn Abi Hathma related to him that the form of the prayer of fear was that the imam stood with a group of his companions, while another group faced the enemy. The imam prayed one raka with them, including the prostration, and then stood. He remained standing while they completed the remaining raka by themselves. They then said the taslim, left, and formed up opposite the enemy while the imam remained standing. Then the others who had not prayed came forward and said the takbir behind the imam and he prayed one raka with them, including the prostration. He then said the taslim, while they stood up and prayed the remaining raka by themselves. Then they said the taslim.