Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1163
'Abdullah b. Buhaina reported: The Messenger of Allah (may peace be upon him) led us two rak'ahs of prayer in one of the (obligatory) prayers and then got up and did not sit. and the people stood up along with him. When he finished the prayer and we expected him to pronounce salutation. he said:" Allah is Most Great" while sitting and made two prostrations before salutation and then pronounced (the, final) salutation.