'Angel of God' in the Bible

Then your handmaid said, The word of my lord the king shall now be comfortable: for as an angel of God, so is my lord the king to discern good and bad: therefore the LORD your God will be with you.

To bring about this change of affairs has your 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 has slandered your servant unto my lord the king; but my lord the king is as an angel of God: do therefore what is good in your eyes.