Musannaf Ibn Abi Shayba 3:3945

Hushaym narrated to us, from Ibn ‘Awn, from Ibn Sirin, who said: The Messenger of Allah (peace and blessings of Allah be upon him) used to look at things during prayer, and he would raise his gaze, until the verse was revealed—if it is not this, then I do not know what it is—: "Those who are humble in their prayers." He said: So the Prophet (peace and blessings of Allah be upon him) lowered his head.