Musnad Ahmad 32:215

Yahya narrated to us, Sa’id narrated to us, from Qatadah, that Anas narrated to them, that the Prophet (peace and blessings of Allah be upon him) said: "What is the matter with people who raise their eyes during their prayer?" He said: He spoke severely regarding that, until he said: "They must desist from that, or their sight will surely be snatched away."