Musannaf Ibn Abi Shayba 3:1380

Hushaym narrated to us, he said: Khalid informed us, from Abu Qilabah, that the Messenger of Allah (peace and blessings of Allah be upon him) said to his companions: "Do you recite behind your Imam?" Some said: "Yes," and some said: "No." He said: "If you must do so, then let one of you recite the Opening of the Book (Al-Fatiha) to himself."