This Bible contradiction is from the Skeptic's Annotated Bible.
Amasa's father was Ithra an Israelite.
2 Samuel 17:25 View context
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.
Amasa's father was Jether an Ishmaelite.
1 Chronicles 2:17 View context
And Abigail bare Amasa: and the father of Amasa [was] Jether the Ishmeelite.