Abdullah bin Umar (may Allah be pleased with them both) narrates: During a battle, the Prophet Muhammad (peace be upon him) led the prayer of fear. One group stood behind him in congregation, while the other group stood between the Prophet (peace be upon him) and the enemy. The Prophet (peace be upon him) led this group in one rak'ah, then they moved to the place of the other group, and the other group came to their place. Then the Prophet (peace be upon him) led them in one rak'ah as well, then he concluded the prayer with salam for all of them. Afterwards, both groups completed one rak'ah each on their own.