Ithra an Israelite - Or "Jether the Ishmeelite" 1 Chronicles 2:17. "Ithra" and "Jether" are practically the same names. "Israelite" in the text is wrong. It should be either "Ishmaelite" or "Jezreelite" 2 Samuel 3:2.

Abigail the daughter of Nahash - If Zeruiah and Abigail were Jesse's daughters, the only probable way of reconciling our text with 1 Chronicles 2:16-17, is to suppose that Nahash was Jesse's wife. If Zeruiah and Abigail were only sisters of David by the mother, then Nahash might be the name of her first husband.

Amasa captain of the host - From the account in this verse, it appears that Joab and Amasa were sisters' children, and both nephews to David.

And Absalom made Amasa captain of the host instead of Joab,.... Who was along with David:

which Amasa was a man's son whose name was Ithra, an Israelite; he is called Jether the Ishmaelite, 1 Chronicles 2:17; either because he was an Ishmaelite by birth, and being proselyted to the Jewish religion, was called an Israelite; or rather he was an Israelite by birth, and having sojourned in the land of Ishmael some time, was called an Ishmaelite, as Uriah the Hittite, and others; and when Amasa is called a "man's son", it means a great man, as Kimchi observes:

that went in to Abigail, the daughter of Nahash, sister to Zeruiah,

Joab's mother: so that Joab and Amasa, the generals of David and Absalom, were own cousins, sisters' children, and David uncle to them both; for Abigail and Zeruiah were David's sisters, 1 Chronicles 2:16; children of Jesse, whose name is here called Nahash, having two names, or this was his surname; though others think Nahash is the name of a woman, the wife of Jesse, and that these two sisters had two mothers, but one father; it seems by this expression, "went in to", as if Amasa was not begotten in the conjugal state, but was illegitimate.

Absalom had made Amasa captain over his army instead of Joab, who had remained true to David, and had gone with his king to Mahanaim. Amasa was the son of a man named Jithra, היּשׂראלי, who had gone in to (i.e., had seduced) Abigail, the daughter of Nahash and sister of Zeruiah, Joab's mother. He was therefore an illegitimate cousin of Joab. The description given of Jithra as ישׂראלי is very striking, since there was no reason whatever why it should be stated that Amasa's father was an Israelite. The Seventy have therefore given ὁ Ἰεζραηλίτης, i.e., sprung from Jezreel, where David's wife Ahinoam came from (1 Samuel 27:3); but they have done so apparently from mere conjecture. The true reading is evidently היּשׁמעאלי, an Ishmaelite, according to 1 Chronicles 2:17, where the name is written Jether, a contracted form of Jithra. From the description given of Abigail as a daughter of Nahash and sister of Zeruiah, not of David, some of the earlier commentators have very justly concluded that Abigail and Zeruiah were only step-sisters of David, i.e., daughters of his mother by Nahash and not by Jesse.

And Absalom made Amasa captain of the host instead of Joab: which Amasa was a man's son, whose name was Ithra an Israelite, that went in to Abigail the daughter of {n} Nahash, sister to Zeruiah Joab's mother.

(n) Who was also called Jesse, David's father.

17:25 Nahash - Nahash is the name of Jesse's wife, by whom he had this Abigail, as he had Zeruiah by another wife; so they were sisters by the father, but not by the mother.

Ithra an Israelite: or, Jether an Ishmaelite

Abigail: Heb. Abigal

Nahash: or, Jesse

25. Amasa-By the genealogy it appears that this captain stood in the same relation to David as Joab, both being his nephews. Of course, Amasa was Absalom's cousin, and though himself an Israelite, his father was an Ishmaelite (1Ch 2:17).

Nahash-is thought by some to be another name of Jesse, or according to others, the name of Jesse's wife.

17:22-29 Ahithophel hanged himself for vexation that his counsel was not followed. That will break a proud man's heart which will not break a humble man's sleep. He thought himself in danger, concluding, that, because his counsel was not followed, Absalom's cause would fail; and to prevent a possible public execution, he does justice upon himself. Thus the breath is stopped, and the head laid low, from which nothing could be expected but mischief. Absalom chased his father. But observe how God sometimes makes up to his people that comfort from strangers, which they are disappointed of in their own families. Our King needs not our help; but he assures us, that what we do for the least of his brethren, who are sick, poor, and destitute, shall be accepted and recompensed as if done to himself