9 And Joab said to Amasa, Art thou well, my brother? And Joab took Amasa by the beard with the right hand to kiss him. 10 And Amasa had taken no notice of the sword that was in Joab's hand: so he smote him with it in the belly and shed out his bowels to the ground, and struck him not again; and he died. And Joab and Abishai his brother pursued after Sheba the son of Bichri.

Matthew Henry's Commentary on 2 Samuel 20:9-10

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.