Jether the Ishmeelite - See the marginal note and reference.

Jether the Ishmeelite - "They called him Jether, because he girded himself with his sword, that he might assist David with the Arabians, when Abner was endeavoring to destroy David and the whole race of Jesse, as being unfit to enter into the congregation of the Lord, on account of Ruth the Moabitess." - T.

And Abigail bare Amasa,.... Who was Absalom's general, afterwards reconciled to David, and designed to be made general of his army, but was slain by Joab, see 2-Samuel 17:25,
and the father of Amasa was Jether the Ishmaelite; he is called an Israelite, 2-Samuel 17:25, and so in the Targum here, he being either a proselyte, or else he was an Israelite by birth, but called an Ishmaelite, because he had dwelt among the Ishmaelites some time, as Obededom is called the Gittite for the like reason; so Jarchi and Kimchi interpret it.

Jether the Ishmaelite--(compare 2-Samuel 17:25). In that passage he is called Ithra an Israelite; and there seems no reason why, in the early days of David, anyone should be specially distinguished as an Israelite. The presumption is in favor of the reading followed by the Septuagint, which calls him "Jetra the Jezreelite." The circumstance of his settling in another tribe, or of a woman marrying out of her own tribe, was sufficiently rare and singular to call for the statement that Abigail was married to a man of Jezreel.

Ishmaelite - By birth or habitation, but by profession an Israelite, 2-Samuel 17:25.