Musannaf Ibn Abi Shaybah

Hazrat Sahl bin Abi Hathmah, regarding the prayer of fear (Salat al-Khawf), says that the Imam will stand facing the Qiblah and a group will pray with him, while the other group will stand facing the enemy. He will lead this group in one rak'ah. When he stands for the second rak'ah, he will remain standing until the group behind him completes their one rak'ah, performs sajdah, and says salam. Then these people will go towards the enemy, and the group already present with the enemy will come and stand behind the Imam. The Imam will lead them in one rak'ah and then say salam. After that, these people themselves will perform ruku', sajdah, and say salam.