Musannaf Ibn Abi Shaybah

Hazrat Abu Alia narrates that Hazrat Abu Musa Ashari was in a region of Isfahan. He did not have much fear of the enemy, but he wanted to teach the people about religion and the Sunnah of the Prophet (peace and blessings be upon him). So he formed two groups of people: he made one group stand armed in front of the enemy, and kept the other group behind him. He led the group behind him in one rak‘ah (unit of prayer), then he, walking backwards, went to the place of the other group in front of the enemy. Then that group came and stood behind Hazrat Abu Musa, and he led this group in the second rak‘ah. Then he said the salam (ending the prayer). Then those who had performed the first rak‘ah and gone to stand before the enemy came and performed one rak‘ah, and the others also performed one rak‘ah. Then they exchanged salam with each other. In this way, the imam completed two rak‘ahs, and both groups performed one rak‘ah each behind the imam.