Mine eye; which words are easily understood both from the nature of the thing, and from the use of this phrase in other scriptures, as Deuteronomy 7:16, Deuteronomy 13:8. The eye is said to spare, because it affects the heart with pity, and moves a man to spare.
Related Commentaries of 1 Samuel 24:10
1 Samuel 24:10
10 Behold, this day thine eyes have seen how that the LORD had delivered thee to day into mine hand in the cave: and some bade me kill thee: but mine eye spared thee; and I said, I will not put forth mine hand against my lord; for he is the LORD'S anointed.