Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
The son of Bichri ... - Rather, "a Bichrite," formed like the names "Ahohite," "Hachmonite," etc. Sa2 23:8-9, and so called from Becher, the son of Benjamin Gen 46:21; Ch1 7:6-8 Saul was also of this family. It is evident that the transfer of the royalty from their tribe to that of Judah still rankled in the hearts of many Benjamites (Sa2 16:8 note).
From Jordan ... - The men of Israel only escorted David from Jordan to Gilgal, and there left him; but the men of Judah in a body went with him all the way to Jerusalem.
To Amasa ... - Evidently feeling his way toward fulfilling the promise to Amasa (marginal reference).
He tarried - The cause of Amasa's delay is not stated. It may have been the unwillingness of the men of Judah to place themselves under his orders, or it may have been caused by a wavering or hesitation in loyalty. This last is evidently insinuated in Sa2 20:11, and no doubt this was the pretext, whether grounded in fact or not, by which Joab justified the murder of Amasa before David.
To Abishai - Probably, as the king was on bad terms with Joab, and wished to deprive him of his post as Captain of the host, he gave his orders to Abishai, and weakly connived at the execution of them by Joab, which was inevitable.
Amasa went before them - Rather, "advanced to meet them." Amasa was no doubt returning to Jerusalem, according to his orders Sa2 20:4, and was probably much surprised to meet the army in march. Joab's resolution was quickly taken.
And Joab's garment ... - Render, "And Joab was girded with his military garment, as his clothing, and upon it" - i. e., the military garment - (or "him"), "the girdle of a sword fastened on his loins in its sheath, and as he went forth" (to meet Amasa) "it fell" out of the sheath. What appears to have happened is that, by accident or design, Joab's sword fell out of the scabbard on the ground as he was going to meet Amasa, and that he picked it up with his left hand so as to have his right hand free for the customary salutation Sa2 20:9. This awakened no suspicion in Amasa's mind. Compare the case of Ehud, Jdg 3:21.
He that favoreth Joab ... - This speech, addressed to Amasa's followers as well as Joab's, shows very distinctly that the rivalry between Joab and Amasa, and David's purpose to make Amasa captain in Joab's room, were well known; and shows also the real reason why Joab killed Amasa. What is added, "and he that is for David," was intended to identify Joab's cause with David's, and also to insinuate that Amasa had not been loyal to David (Sa2 20:5 note).
All the people ... - i. e., the levies which Amanda had been leading to Jerusalem; they were irresolute as to what they should do, and the stoppage at Amasa's body very nearly led to their refusing to follow Joab. But upon the prompt removal and hiding of the body they passed on and followed Joab, their old captain.
Abel - More commonly called Sa2 20:15 "Abel-Beth-maachah" to distinguish it from other places of the name of "Abel" (a grassy plain). It is represented by the modern Abil-el-Kamh, a Christian village on the northwest of lake Huleh, the ancient Merom. Compare Ch2 16:4, "Abel-maim," Abel by the water.
And all the Berites - What this means is utterly unknown. Many approve of the reading of the Latin Version, connecting it with what follows: "And all the choice young men mustered and followed him."
Cast up a bank - See the marginal references. The throwing up of mounds against the walls of besieged places by the besiegers is well illustrated in the Assyrian sculptures.
The trench - The "pomoerium," or fortified space outside the wall. When the mound was planted in the pomoerium the battering engines were able to approach close to the wall to make a breach.
This was an old proverb. Abel, like Teman, and some other places, was once famous for the wisdom of its inhabitants Kg1 4:30-31. The wise woman was herself a remnant of this traditional wisdom.
I am one ... - The woman speaks in the name of the whole city, which she means to say was peaceable and loyal.
Joab's character is strongly brought out in the transaction. Politic, decided, bold, and unscrupulous, but never needlessly cruel or impulsive, or even revengeful. No life is safe that stands in his way, but from policy he never sacrifices the most insignificant life without a purpose. (Compare Sa2 2:27-30.)
Now Joab ... - This is by no means an unmeaning repetition. Joab had been dismissed to make room for Amasa, and was now, as the result of his successful expedition against Sheba, and the death of Amasa, reinstated in his command. Moreover, this was a fresh beginning of David's reign, and therefore a statement of his chief officers is as proper as in Sa2 8:16, when he had just established himself on the throne of Israel. Compare Kg1 4:2-6.
Adoram - Not mentioned before by name or office. Apparently, therefore, the office was not instituted until the latter part of David's reign, and its duties probably were the collection of the tribute imposed upon vanquished nations, or the command of the forced levies employed in public works. Adoram was stoned to death in the beginning of the reign of Rehoboam Kg1 12:18.
Ira the Jairite - Not mentioned before: perhaps the same as "Ira an Ithrite" (marginal reference), i. e., an inhabitant of Jattir in the hill country of Judah Jos 15:48; Sa1 30:27. Perhaps we ought to read "Ithrite," for "Jairite."
A chief ruler ... about David - More simply and clearly, "was David's kohen" (Sa2 8:18 note). In the early part oph David's reign his own ons were כהן kôhên (chief rulers). The deaths of Amnon and Absalom, and the dissensions in the family, had probably caused the change of policy in this respect.