Salih bin Khawwat (may Allah have mercy on him) narrates from one who prayed the fear prayer with the Prophet (peace and blessings be upon him) at Dhat al-Riqa' that one group formed a row with him (peace and blessings be upon him) and another group remained standing facing the enemy. The group that was with him (peace and blessings be upon him) prayed one rak'ah; then he (peace and blessings be upon him) remained standing while they completed their prayer by themselves, then they left and formed a row facing the enemy. Then the other group came and prayed with him (peace and blessings be upon him) the rak'ah that remained. Then he (peace and blessings be upon him) remained seated while they completed their prayer, then he (peace and blessings be upon him) gave the salam with them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6009
Salih bin Khawwat (may Allah have mercy on him) narrates from his father (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) led the fear prayer. One group was with him (peace and blessings be upon him) and the other was facing the enemy. The Prophet (peace and blessings be upon him) led those who were with him (peace and blessings be upon him) in one rak'ah; then he (peace and blessings be upon him) stood up, and they stood and completed their prayer. Then they went to the place of their companions and the other group came, and the Prophet (peace and blessings be upon him) led them in the one rak'ah that remained; then they completed their prayer. Ubaydullah (may Allah have mercy on him) said that al-Qasim (may Allah have mercy on him) said: I have not heard anything about the fear prayer more beloved to me than this.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6010
Sayyiduna Sahl bin Abi Hathmah (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) led his Companions in the fear prayer and arranged them behind him in two rows. He led the row that was with him (peace and blessings be upon him) in one rak'ah. Then he (peace and blessings be upon him) remained standing until they had prayed one rak'ah. Then those behind came forward and the first row went back. Then the Prophet (peace and blessings be upon him) led them in one rak'ah. Then he (peace and blessings be upon him) sat until those behind had prayed one rak'ah. Then he (peace and blessings be upon him) gave the salam with them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6011
Sahl bin Abi Hathmah (may Allah be pleased with him) said regarding the fear prayer: The imam stands facing the qiblah, one group of them is with the imam and the other group is towards the enemy, with their faces towards the enemy. The imam leads them in one rak'ah, and they perform the bowing and prostrations by themselves, that is, for the second rak'ah. Then they go to the place of the others, and those pray one rak'ah with the imam and then complete the bowing and prostrations of the second rak'ah. In this way the imam will have two rak'ahs and they will have one rak'ah (with him).
In the hadith of Musaddad: Those who prayed one rak'ah with the imam should pray the second rak'ah by themselves.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6012