(10) In the fifth rib= Abdomen. (See Note on 2Samuel 2:23.)

So Joab and Abishai.--Joab here comes forward as the commander of the pursuit without previous mention. He may have accompanied Abishai from Jerusalem, or he may have joined him on the route; but, now, having murdered Amasa, he assumes his old place as commander-in-chief, doubtless with the connivance of his brother.

Verse 10. - In the fifth fib; in the abdomen (see note on 2 Samuel 2:23). He struck him not again. When his sword fell out of its sheath, Joab picked it up with his left hand, which was not the hand for action, and as he could not put it into its place without taking it into his right hand, his continuing to hold it while he took his cousin's beard in his fight hand and kissed him, was too natural to awaken any suspicion. But holding down Amasa's head, he struck him with his left hand so fiercely that no second blow was necessary; and then continued his march forward as if what had occurred was a matter of little importance.

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.But Amasa took no heed to the sword that was in Joab's hand,.... In his left hand, for with his right hand he took him by the beard; he might see the sword drop out of the scabbard, and Joab take it up, which he supposed he did in order to put it into its sheath again, having no suspicion of his wicked design, and therefore not at all upon his guard to prevent it:

so he smote him therewith in the fifth rib; in the same place where Abner smote Asahel, and Joab Abner; See Gill on 2 Samuel 2:23 and See Gill on 2 Samuel 3:27, he must strike him, as some observe, on the left side, because he was embracing him; and the stroke must be deadly, because he struck him in the pericardium, which surrounds the heart round with water, to refrigerate it; for the lower part of the heart reaches to the fifth rib; see John 19:34 (u):

and shed out his bowels to the ground; which fell out through the incision made by the sword:

and struck him not again: he gave him such a home thrust, there was no need to repeat it, he dispatched him at once:

and he died; and thus, though he was pardoned by David, and promoted to honour by him, yet the providence of God would not suffer him to go unpunished for joining with Absalom in an unnatural rebellion against his uncle:

so Joab and Abishai his brother pursued after Sheba the son of Bichri: for Amasa being slain, Joab without any ceremony reassumed his post as general, and, with his brother Abishai under him, made all the haste they could in pursuit of the rebel.

(u) Weemse's Portrait of Man, p. 25.