Midrash sur Samuel 2 3:2

Abraham begot Isaac (Gen. 25:19). R. Isaac stated; No generation lacks scoffers. While Nabal was shearing his flock, David sent some of his young men to him with the request: Give, I pray thee, whatsoever cometh to thy hand, unto thy servants, and to thy son David (I Sam. 25:8). But Nabal retorted: Who is David? And who is the son of Jesse? There are many servants nowadays that break away every man from his master; shall I then take my bread and my water and my flesh that I have killed for my shearers and give it unto men of whom I know not whence they are? (ibid., vv. 10–11). When David’s men returned and repeated Nabal’s words, he armed himself and his soldiers, and with their weapons started out to destroy Nabal. But one of the young men told Abigail, Nabal’s wife, saying: “Behold, David sent messengers out of the wilderness to salute our master; but he hath spoken rudely to them” (ibid., v. 14). As soon as she heard what had transpired, she prepared a gift which she took to David, as it is said: Then Abigail made haste, and took two hundred loaves, and two bottles of wine, and five sheep ready dressed, and five measures of corn … and she said unto her men: “Go on before me; I come after you.” But she told not her husband Nabal (ibid., vv. 18–19). Later on Scripture states: And it came to pass about ten days later, that the Lord smote Nabal so that he died…. and David sent and spoke unto Abigail to take her to him to wife (ibid. 38:39). After he had her brought to him, David stayed apart from her for three months to determine whether or not she had conceived with Nabal. After the third month, David had intercourse with her and she became pregnant. The scoffers in that generation asserted that she had actually conceived from Nabal. What did the Holy One, blessed be He, do? He ordered the angel in charge of the formation of embryos to fashion that embryo in the likeness of its father so that everyone would be forced to acknowledge that David was the father. We know that this is so from the verse And his firstborn was Amnon, of Ahinoam the Jezreelitess, and his second, Chileab, of Abigail, the wife of Nabal the Carmelite (II Sam. 3:2). Why does Scripture call him Chileab (khilav)? Because he was completely like his father (kulo av), and everyone who saw him said: “David is this child’s father.”