Adam Clarke on 1 Samuel 11:2

I may thrust out all your right eves - This cruel condition would serve at once as a badge of their slavery, and a means of incapacitating them from being effective warriors. Theodoret observes, "He who opposes his shield to the enemy with his left hand, thereby hides his left eye, and looks at his enemy with his right eye; he therefore who plucks out that right eye makes men useless in war." Josephus gives the same reason.