Musnad Abu Ya'la al-Mawsili 115:77

Abu Bakr narrated to us, Muhammad ibn Bishr narrated to us, from Sa'id, from Qatadah, from Anas, from the Prophet (peace be upon him), who said: "What is the matter with people who raise their eyes toward the sky during their prayer?" His speech regarding that became severe, until he said: "They must desist from that, or their eyesight will surely be snatched away."