As an angel of God - Rather, as “the” Angel of God; and therefore whatever David decided would be right.
Related Commentaries of 2 Samuel 14:17
2 Samuel 14:17
17 Then thine handmaid said, The word of my lord the king shall now be comfortable:c for as an angel of God, so is my lord the king to discern good and bad: therefore the LORD thy God will be with thee.