Abigail bore Amasa; and the father of Amasa was Jether the Ishmaelite.
1 Chronicles 2:17
Surrounding context
2:16 Now their sisters were Zeruiah and Abigail. And the sons of Zeruiah were Abishai, Joab, and Asahel--three.
2:17 Abigail bore Amasa; and the father of Amasa was Jether the Ishmaelite.
2:18 Caleb the son of Hezron had children by Azubah, his wife, and by Jerioth. Now these were her sons: Jesher, Shobab, and Ardon.