New Defender's Study Bible Notes
21:1 the days of David. The chronological history of David’s life and reign is given in I Samuel 16–II Samuel 20. The last four chapters of II Samuel are in the nature of appendices.
21:1 slew the Gibeonites. Joshua had made a firm commitment to the Gibeonites four hundred years earlier (Joshua 9:15), and Saul and his sons had broken that treaty. This act is not recorded elsewhere in Scripture, but apparently had grievously displeased the Lord.
21:6 of his sons. It is probable that these seven sons were as guilty as their father in the unwarranted slaughter of the Gibeonites (II Samuel 21:1-6), which had resulted in a divinely-sent famine on Israel. Note the mention of “Saul, and for his bloody house, because he slew the Gibeonites” in II Samuel 21:1.
21:8 five sons of Michal. Michal was without children of her own (II Samuel 6:23), but apparently raised the five sons of Adriel, her brother-in-law, who had been married to her sister Merab (I Samuel 18:19).
21:19 slew the brother of Goliath. Since the words “the brother of” are not in the original (and, therefore, are italicized in most printings of the King James Version), critics have alleged a contradiction here with the story of David and Goliath (I Samuel 17:4,7,50). It is more reasonable, however, to assume an ancient copyist omission here, especially in view of the more complete description given in the parallel passage, as follows: “And there was war again with the Philistines; and Elhanan the son of Jair slew Lahmi the brother of Goliath the Gittite, whose spear staff was like a weaver’s beam” (I Chronicles 20:5). Another (less likely) resolution would be the possibility that this Goliath was the son of the Goliath slain by David, and that both Goliath (Jr.) and his brother Lahmi were slain by Elhanan. In either case, there is no contradiction.
21:22 born to the giant. The campaign described in these verses apparently marked the final extermination of the giants of Canaan.