Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) ordered the fear prayer. The Messenger of Allah (peace and blessings be upon him) stood, and we formed two rows behind him (peace and blessings be upon him). He (peace and blessings be upon him) said the takbir, and all of us, that is, both rows, bowed together. Then he (peace and blessings be upon him) raised his head and prostrated, and the first row prostrated with him (peace and blessings be upon him) while the second row remained standing, guarding their brothers. When he (peace and blessings be upon him) had finished his prostration and stood up, those of the rear row made their prostrations. Then they stood up. Then the first row moved back and the second row came forward. Then he (peace and blessings be upon him) bowed, and everyone bowed with him (peace and blessings be upon him), and the Messenger of Allah (peace and blessings be upon him) prostrated, and those of the first row prostrated with him (peace and blessings be upon him). Those of the second row remained standing, guarding their brothers. Then the Messenger of Allah (peace and blessings be upon him) remained seated, and those of the second row prostrated. Then the Prophet (peace and blessings be upon him) gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6031