'Angel of God' in the Bible

Then thy handmaid said, Let, I pray thee, the word of my lord the king be comfortable; for as an angel of God, so is my lord the king to discern good and bad: and Jehovah thy God be with thee.

to change the face of the matter hath thy servant Joab done this thing: and my lord is wise, according to the wisdom of an angel of God, to know all things that are in the earth.

And he hath slandered thy servant unto my lord the king; but my lord the king is as an angel of God: do therefore what is good in thine eyes.