2 Samuel 17:25

Now Absalom had set Amasa over the army instead of Joab . Amasa was the son of a man named Ithra the Ishmaelite , who had married Abigal the daughter of Nahash , sister of Zeruiah , Joab’s mother .

Absalom had appointed Amasa over the army in place of Joab. Amasa was the son of Jether, an Ishmaelite who had married Abigail, the daughter of Nahash and sister of Zeruiah the mother of Joab.

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 Nahash, sister to Zeruiah Joab's mother.