Mishkat al-Masabih #958

‘Abdallah ibn Buhaina said that the Prophet led them in the noon prayer, and when he stood up at the end of the first two rak'as and did not sit, the people stood up along with him. When he finished the prayer and the people expected him to give the salutation, he said “God is most great" while sitting and made two prostrations before giving the salutation. Then he gave it. (Bukhari and Muslim.)