It was narrated that Ibn 'Umar said:
"The Messenger of Allah (ﷺ)
said:
'Do not lift your gaze to the heavens lest your sight be
snatched away," meaning during prayer. (DE)
English reference (DE): Vol. 1, Book 5, Hadith 1043 (DE)
Arabic reference (DE): Book 5, Hadith 1096 (DE)