Abdur Rahman bin Mahdi عبد الرحمن بن مهدي · The Book of Forgetfulness (In Prayer)

A man from among the companions of the Prophet (ﷺ) told him that he heard the Messenger of Allah (ﷺ) say: 'If any one of you in praying, let him not lift his gaze to the sky, or his eyesight will be taken away.'"

"I heard Abu Al-Ahwas saying to us in a gathering with Ibn Al-Musayyab when Ibn Al-Musayyab was sitting there, that he had heard Abu Dharr say: The Messenger of Allah (ﷺ) said: "Allah (SWT) continues to look upon His slave while he is praying, so long as he does not turn away. If he turns his face away, He turns away from him."

"I asked the Messenger of Allah (ﷺ) about looking here and there during prayer. He said: 'That is something that the Shaitan snatches from one's prayer.'"

The Prophet (ﷺ) said: "It is as if I can see the whiteness of his cheek, saying to his right: As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) and to his left: As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah)." (Sahih