(9) باب النَّهْىِ عَنْ رَفْعِ الْبَصَرِ، إِلَى السَّمَاءِ فِي الصَّلاَةِ
It was narrated from Anas bin Malik that:
The Messenger of Allah (ﷺ) said: "What is the matter with people who lift their gaze to the sky when praying?" And he spoke sternly concerning that until he said: "They must stop that or they will certainly lose their eyesight."
Reference: Sunan an-Nasa'i 1193
In-book reference: Book 13, Hadith 15
English translation: Vol. 2, Book 13, Hadith 1194