Merab, daughter of Saul: Midrash and Aggadah
Merab was Saul’s eldest daughter. According to the Bible, she was meant to marry David, but she was given in matrimony to Adriel the Meholathite, while David married Merab’s younger sister Michal. Despite the Biblical account, some Rabbis believe that Saul’s original plan was brought to fruition and that David married both sisters. This tradition may be based on a reading of I Sam. 18:21: “So Saul said to David, ‘You can become my son-in-law even now through the second one [or: by two (bi-shtayim)],” understanding “bi-shtayim” as “by [my] two [daughters].” According to this view, Merab was properly married to David and her marriage to Adriel the Meholathite was sinful, just as her sister Michal was married to David and wrongfully given to Paltiel son of Laish (T Sotah [ed. Lieberman] 11:17).
The Rabbis ask how David could have married two sisters, a situation that is prohibited by the halakhah, and answer that David first married Merab and after her death married Michal (T Sotah, halakhah 18). A different Rabbinic position, however, denies that David married Merab; her betrothal to him was contracted in error, and therefore halakhically invalid. Saul promised that the man who would smite Goliath the Philistine would receive a great sum of money and also his daughter. David did indeed kill the Philistine champion, but Saul did not keep his promise. He explained this by telling David that one may not betroth a woman by way of fulfilling a debt. He said “I am indebted to you, and if one betroths a woman by [way of repaying] a debt, the betrothal is not in force.” Saul then gave Merab to Adriel. Thus, according to this position, the betrothal was erroneous, David never married Merab, and there was no problem of marriage to two sisters (BT Sanhedrin 19b).
The Rabbis state that Merab died after bearing five sons to Adriel the Meholathite and Michal raised her dead sister’s children as if they were her own. This tradition seeks to resolve the contradiction between I Sam. 18:19, according to which Merab married Adriel the Meholathite, and II Sam. 21:8, that tells of Michal’s marriage to Adriel and the five sons that she bore him. The Rabbis explain that these were Merab’s children, but were attributed to Michal because she raised them (T Sotah [ed. Lieberman] 11:20; JT Kiddushin 4:1, 65b).
See also: Michal Daughter of Saul.