Musnad Abu Ya'la al-Mawsili 115:320

Abu Musa narrated to us, Ibn Abi Adi and Abd al-A’la narrated to us, from Sa’id, from Qatadah, from Anas, that the Prophet of Allah (peace be upon him) 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 cease from that, or their sight will surely be snatched away."