1 Samuel 12:12-13 NASB
12 When you saw that Nahash the king of the sons of Ammon came against you, you said to me, 'No, but a king shall reign over us,' although the Lord your God was your king. 12 Now therefore, here is the king whom you have chosen, whom you have asked for, and behold, the Lord has set a king over you.
But in 2 Samuel 17:25 (NIV), it's said that that same Abigail (both having a son named Amasa with an Ishmaelite named Jether; both having a sister named Zeruiah with a son named Joab) was the daughter of "Nahash":
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.