Adam Clarke on 2 Samuel 14:11

Let the king remember the Lord thy God - Consider that when God is earnestly requested to show mercy, he does it in the promptest manner; he does not wait till the case is hopeless: the danger to which my son is exposed is imminent; if the king do not decide the business instantly, it may be too late.

And he said, As the Lord liveth - Thus he binds himself by a most solemn promise and oath; and this is what the woman wanted to extort.