8 When they were at the great stone which is in Gibeon, Amasa came before them. And Joab was girded with his coat, his dress, and upon it was the girdle of the sword which was fastened on his loins in its sheath; and as he went forth it fell out.

Matthew Henry's Commentary on 2 Samuel 20:8

Commentary on 2 Samuel 20:4-13

(Read 2 Samuel 20:4-13)

Joab barbarously murdered Amasa. The more plot there is in a sin, the worse it is. Joab contentedly sacrificed the interest both of the king and the kingdom to his personal revenge. But one would wonder with what face a murderer could pursue a traitor; and how, under such a load of guilt, he had courage to enter upon danger: his conscience was seared.