1 And when Saul's son heard that Abner was dead in Hebron, his hands were feeble, and all the Israelites were troubled. 2 And Saul's son had two men who were captains of bands: the name of one was Baanah and the name of the other Rechab, the sons of Rimmon a Beerothite, of the children of Benjamin (for Beeroth also was reckoned to Benjamin, 3 And the Beerothites fled to Gittaim and have been sojourners there until this day).
4 And Jonathan, Saul's son, had a son who was lame of his feet. He was five years old when the tidings of Saul and Jonathan came out of Jezreel, and his nurse took him up and fled. And it came to pass, as she made haste to flee, that he fell and became lame. And his name was Mephibosheth.
5 And the sons of Rimmon the Beerothite, Rechab and Baanah, went and came at about the heat of the day to the house of Ish-bosheth, who lay on a bed at noon. 6 And they came there into the midst of the house, as though they would have fetched wheat, and they smote him under the fifth rib. And Rechab and Baanah his brother escaped. 7 For when they came into the house, he lay on his bed in his bed-chamber, and they smote him, slew him, beheaded him, and took his head and went away through the plain all night. 8 And they brought the head of Ish-bosheth to David to Hebron and said to the king, "Behold the head of Ish-bosheth the son of Saul your enemy, who sought your life. And the LORD has avenged my lord the king this day of Saul and of his seed."
9 And David answered Rechab and Baanah his brother, the sons of Rimmon the Beerothite, and said to them, "As the LORD lives, who has redeemed my soul out of all adversity, 10 When someone told me, saying, 'Behold, Saul is dead,' (thinking to have brought good tidings), I took hold of him and slew him in Ziklag, who thought that I would have given him a reward for his tidings. 11 How much more, when wicked men have slain a righteous person in his own house upon his bed? Shall I not therefore now require his blood of your hand and take you away from the earth?" 12 And David commanded his young men, and they slew them, cut off their hands and their feet, and hanged them over the pool in Hebron. But they took the head of Ish-bosheth and buried it in the sepulcher of Abner in Hebron.
[v.1] - "Abner was dead" - Reference, 2nd Samuel 3:27.
[v.2] - "Beeroth also was reckoned to Benjamin" - Reference, Joshua 18:21-25.
[v.4] - "the tidings of Saul and Jonathan" - Reference, 1st Samuel, ch. 31.
[v.10] - Rechab and Baanah think themselves doing David a favor by killing a descendant of Saul; therefore eliminating a contender for the throne. It was common for a transfer of power from one king to another to invoke a lot of bloodshed, especially for the descendants of the former king, whether for good or for bad (e.g., Zimri killing the house of Baasha when he took the throne in 1st Kings 16:8-11, Jehu slaying the house of Ahab in 2nd Kings, ch. 10, etc.). David, on the other hand, seems to be waiting for the Lord to appoint him as king when the Lord wishes it to be. To show his obedience to the Lord, David keeps himself from killing or arranging the deaths of the sons of Saul. He had made a covenant with Saul at the cave in the wilderness of Engedi that he would spare the seed, or sons, of Saul and would not destroy the name of the house of Saul's father (1st Samuel 24:21-22). David acknowledges his covenant and desires to keep it. David surely is remembering the law of Moses, which says, "When you vow a vow to the LORD your God, you shall not defer to pay it, for the LORD your God will surely require it of you, and it would be sin in you. But if you forbear to vow, it shall be no sin in you. That which is uttered by your lips you shall keep and perform, even a free-will-offering, according as you have vowed to the LORD your God, which you have promised with your mouth" (Deuteronomy 23:21-23).