Musnad Ahmad 776:1

Muhammad ibn Abi ‘Adi narrated to us, from al-Hajjaj—meaning al-Sawwaf—from Abi ‘Uthman, from Yahya ibn Abi Kathir, from ‘Abdullah ibn Abi Qatadah and Abu Salamah, from Abu Qatadah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) used to lead us in prayer. In the Dhuhr and ‘Asr prayers, he would recite in the first two rak'ahs the Opening of the Book (al-Fatihah) and two surahs, and he would let us hear the verse sometimes. He used to prolong the first rak'ah of the Dhuhr prayer and shorten the second, and likewise in the morning (Fajr) prayer.