John Gill Commentary 2 Samuel 14:20

"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." — 2 Samuel 14:20 (ASV)

To fetch about this form of speech has your servant Joab done
this thing

Feigned a story in such form and manner as had been delivered to the king, that it might be accommodated and applied to the case of Absalom, and to transfer it in a figure to the king, to use the apostle's phrase, (1 Corinthians 4:8) ;

and my lord [is] wise, according to the wisdom of an angel of God ;

as not only to understand the design of this fable or parable, but of such sagacity and penetration as to find out the author of it; and even

to know all [things] that [are] in the earth ;

either in the whole world, or rather in the land of Israel; and it is to be understood not of all actions natural and moral done by men in it, which would be to ascribe omniscience to him; but of all political things, all things respecting civil government; that he had such a spirit of discerning of men and things, that nothing could be said or done, or scheme formed, but he got intelligence of it, and insight into it; and which was carrying the compliment to a great height.