﴿ قُل لِّلْمُؤْمِنِينَ يَغُضُّوا۟ مِنْ أَبْصَٰرِهِمْ وَيَحْفَظُوا۟ فُرُوجَهُمْ ۚ ذَٰلِكَ أَزْكَىٰ لَهُمْ ۗ إِنَّ ٱللَّهَ خَبِيرٌۢ بِمَا يَصْنَعُونَ ﴾

“Tell the believing men to lower their gaze and to be mindful of their chastity: this will be most con­ducive to their purity – [and,] verily, God is aware of all that they do.”

Tell believing men to lower their gaze from what is unlawful for them to look at min of min absārihim ‘their gaze’ is extra and to guard their private parts from doing with them what is unlawful for them to do. That is purer in other words better for them. Truly God is Aware of what they do with their gazes and private parts and He will requite them for it.