2 Samuel 14:9

The iniquity be on me. Technically the murderer was guilty, but because of the circumstances David was granting him a reprieve. The woman had gained her point but wished to prolong the discussion so as to make David commit himself further. To do this, she asked that if there were any blood guilt, it be permitted to rest on her and not on David and his throne. In doing this she skillfully drew David into the position where he himself would assume the responsibility. Thus far he had simply put her off with a promise without specifically involving himself.