Albert Barnes Commentary 2 Samuel 14:9

"And the woman of Tekoa said unto the king, My lord, O king, the iniquity be on me, and on my father`s house; and the king and his throne be guiltless." — 2 Samuel 14:9 (ASV)

The iniquity be on me ... - Compare the principle in Genesis 9:5-6 and Numbers 35:30-34. The woman therefore says that if there is any guilt in sparing her son, may it rest upon her and her house, not on David and his throne (compare 2 Samuel 3:28). The woman's cunning speech extracted a more direct promise of protection from the king (2 Samuel 14:1).