Musnad Abu Ya'la al-Mawsili 115:287

Ubayd Allah narrated to us, Yahya ibn Sa'id narrated to us, from Hisham, Qatadah narrated to us, from Anas: That the Prophet (peace and blessings of Allah be upon him), Abu Bakr, Umar, and Uthman used to begin the recitation with "Al-hamdu lillahi rabbil-'alamin" (All praise is due to Allah, Lord of the worlds).