The prohibition of lifting one's gaze to the sky when praying
أَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، عَنْ يُونُسَ، عَنِ ابْنِ شِهَابٍ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، أَنَّ رَجُلاً، مِنْ أَصْحَابِ النَّبِيِّ صلى الله عليه وسلم حَدَّثَهُ أَنَّهُ سَمِعَ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " إِذَا كَانَ أَحَدُكُمْ فِي الصَّلاَةِ فَلاَ يَرْفَعْ بَصَرَهُ إِلَى السَّمَاءِ أَنْ يُلْتَمَعَ بَصَرُهُ " .
It was narrated from 'Ubaidullah bin Abdullah that: 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.'"