Sisters - i. e. half-sisters. Abigail and Zeruiah were daughters not of Jesse, but of a certain Nahash, whose widow Jesse took to wife 2 Samuel 17:25.

From the present passage, and from the fact that Abishai joined David as a comrade in arms before Joab 1 Samuel 26:6, it would seem that, although Joab was pre-eminent among the three 2 Samuel 2:13, 2 Samuel 2:16, Abishai was the eldest.

Whose sisters were Zeruiah and Abigail..... That is, sisters of David:

and the sons of Zeruiah; Abishai, and Joab, and Asahel, three; all valiant men and captains in David's army; their father's name is nowhere mentioned.

The sisters of David have become known through their heroic sons. Zeruiah is the mother of the heroes of the Davidic history, Abishai, Joab, and Asahel (cf. 1 Samuel 26:6; 2 Samuel 2:18; 2 Samuel 3:39; 2 Samuel 8:16, and elsewhere). Their father is nowhere mentioned, "because their more famous mother challenged the greater attention" (Berth.). Abigail was, according to 2 Samuel 17:25, the daughter of Nahash, a sister of Zeruiah, and so was only a half-sister of David, and was the mother of Amasa the captain of the host, so well known on account of his share in the conspiracy of Absalom; cf. 2 Samuel 17:25; 2 Samuel 19:14, and 2 Samuel 20:10. His father was Jether, or Jithra, the Ishmaelite, who in the Masoretic text of 2 Samuel 17:25 is called, through a copyist's, error, היּשׂראלי instead of היּשׁמעאלי; see comm. on passage.

Whose sisters were Zeruiah, and Abigail. And the sons of Zeruiah; Abishai, and Joab, and Asahel, three.

2:1-55 Genealogies. - We are now come to the register of the children of Israel, that distinguished people, who were to dwell alone, and not be reckoned among the nations. But now, in Christ, all are welcome to his salvation who come to him; all have equal privileges according to their faith in him, their love and devotedness to him. All that is truly valuable consists in the favour, peace, and image of God, and a life spent to his glory, in promoting the welfare of our fellow-creatures.