פירוש על עבודה זרה 40:1

This baraita seems to say that one cannot look at anything that might be sexually enticing. This includes any woman and even at animals (and even ugly ones) when they are mating. One should guard oneself constantly against stirring up desire. This would obviously be a very hard rule to observe in the modern age. The angel of death evidently has eyes everywhere. Even if a human had this many eyes and could not help seeing everything, he still should make sure he does not look at anything improper.