It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Salat al-Khawf (prayer of fear) used to be performed in the same way as nowadays your guards pray behind your imams. However, what used to happen was that the army would be in the mountain passes, and a group of people would stand; all of them would be with the Prophet (peace and blessings be upon him). When one group with the Prophet (peace and blessings be upon him) had completed the prostration, the Prophet (peace and blessings be upon him) would stand up, and the group that was standing would perform the prostration themselves. Then, when the Prophet (peace and blessings be upon him) would stand, all would stand. Then the Prophet (peace and blessings be upon him) would bow (ruku‘), and all the people would bow as well. When the Prophet (peace and blessings be upon him) would prostrate, those who had stood the first time would join him in prostration, and those who had prostrated with the Prophet (peace and blessings be upon him) the first time would stand up. When the Prophet (peace and blessings be upon him) would sit, and those who had prostrated with him at the end would also sit, then those who were standing would perform the prostration. Then they would sit, and the Prophet (peace and blessings be upon him) would conclude the prayer with salam, gathering all of them together.