Fausset's Bible Dictionary
("father of joy".)
1. The churl Nabal's beautiful wife, of Carmel. Taking on herself the blame of Nabal's insult to David's messengers, she promptly, and with a discreet woman's tact, averted David's just anger by liberally supplying the wants of his forces, and by deprecating in person at his feet the shedding of blood in vengeance. He hearkened to her prayer and accepted her person; and rejoiced at being "kept back" by her counsel from taking into his own hand God's prerogative of vengeance (1 Samuel 25:26; 1 Samuel 25:34; 1 Samuel 25:39; compare Romans 12:19). God did "plead His cause" against Nabal: compare the undesigned coincidence of phrase between the history and the independent psalm, a proof of genuineness: Psalms 35:1; Psalms 7:16; Psalms 17:4; Psalms 14:1 with 1 Samuel 25:25; 1 Samuel 25:36-38 with Luke 12:19-21; 1 Samuel 25:29; the image of a "sling, slinging out the souls of the enemy" with 1 Samuel 17:49. At Nabal's death by God's visitation David made her his wife, and by her David had a son, Chileab (2 Samuel 3:3), or Daniel (1 Chronicles 3:1), i.e. God is my judge, a name which apparently alludes to the divine judgment on Nabal.
2. A sister of David, daughter of Nahash; wife of Jether or Ithra, an Ishmaelite, rather seduced by him (See ); mother of Amasa (1 Chronicles 2:15-17). David was probably her and Zeruiah's half brother, born of the same mother, but he having Jesse, she and Zeruiah Nahash, for their father. This accounts for the phrase "Abigail, daughter of Nahash, and sister of Zeruiah," not of David. Zeruiah and she were only his step-sisters.
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Fausset, Andrew R. Entry for 'Abigail'. Fausset's Bible Dictionary. https://www.studylight.org/dictionaries/eng/fbd/a/abigail.html. 1949.