Sahih Muslim Book 4, Hadith Number 912.

Chapter : Recitation of the Qur’an loudly in the dawn prayer.

Jabir b. Samura reported: The people of Kufa complained to Umar b. Khattab about Sa’id and they made a mention of his prayer. ‘Umar sent for him. He came to him. He (‘Umar) told him that the people had found fault with his prayer. He said: I lead them in prayer in accordance with the prayer of the Messenger of Allah (may peace be upon him). I make no decrease in it. I make them stand for a longer time in the first two (rak’ahs) and shorten it in the last two. Upon this ‘Umar remarked: This is what I deemed of thee, O Abu Ishaq