Musnad Ahmad 1007:111

Yazid ibn Harun narrated to us, Hammam ibn Yahya and Aban ibn Yazid informed us, from Yahya ibn Abi Kathir, from Abdullah ibn Abi Qatadah, from his father, that the Messenger of Allah (peace and blessings of Allah be upon him) used to: "Recite in the first two rak'ahs of the Dhuhr and the 'Asr [prayers] the Opening of the Book (Al-Fatihah) and a surah, and he would let us hear the verse sometimes. And he would recite in the last two rak'ahs the Opening of the Book (Al-Fatihah)."