Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) said: The Prophet (peace and blessings be upon him) stood, and the people stood with him (peace and blessings be upon him). Then he (peace and blessings be upon him) said the takbir, and the people also said the takbir with him (peace and blessings be upon him). He (peace and blessings be upon him) bowed, and the people bowed with him (peace and blessings be upon him). Then he (peace and blessings be upon him) prostrated and the people also prostrated. Then he stood up for the second rak'ah, and those who had prostrated with him (peace and blessings be upon him) moved back and guarded their brothers. Then the other group performed the bowing and prostrations with the Prophet (peace and blessings be upon him). All the people were in prayer, saying the takbir, and they were guarding one another.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6029