I asked Messenger of Allah ﷺ about the sudden glance (that is cast) on the face (of a non-Mahram). He commanded me that I should turn away my eyes. (Using translation from Muslim 2159a)
سَأَلْتُ النَّبِيَّ ﷺ عَنْ نَظْرَةِ الْفُجَاءَةِ فَأَمَرَنِي أَنْ أَصْرِفَ بَصَرِي