Musnad Ahmad 1007:81

Abu al-Mughirah narrated to us, al-Awza'i narrated to us, Yahya ibn Abi Kathir narrated to us, from Abdullah ibn Abi Qatadah, from his father, that the Prophet, peace and blessings of Allah be upon him, used to: "Recite the Mother of the Quran (Al-Fatihah) and two surahs along with it in the first two rak'ahs of the Dhuhr and Asr prayers, and he would let us hear the verse sometimes. And he used to prolong the first rak'ah."