Musnad Ahmad Hadith 14436

It is narrated from Jabir (may Allah be pleased with him) that he had the opportunity to perform the prayer of fear (Salat al-Khawf) with the Prophet (ﷺ). At that time, the enemy was positioned between us and the Qiblah. We formed two rows behind the Prophet (ﷺ). The Prophet (ﷺ) said the takbir and we also said the takbir with him. Then he bowed (in ruku‘) and we all bowed with him. Then, when he raised his head from ruku‘ and went into prostration (sajdah), only those in the first row performed sajdah with him, while the second row remained standing in front of the enemy. When the Prophet (ﷺ) and those in the first row stood up, the people in the back row went into sajdah. After that, the people in the back row came forward and the people in the front row moved to the back. Then we all bowed together, and when the Prophet (ﷺ) performed sajdah, the first row also performed sajdah, and when they sat, the people in the back row also performed sajdah, and all of us ended the prayer together with salam, just as nowadays your security detachments do with their commanders.