23 Then King Solomon swore by the LORD: “May God deal with me, be it ever so severely, if Adonijah does not pay with his life for this request!

Read 1 Kings 2:23 Using Other Translations

Then king Solomon sware by the LORD, saying, God do so to me, and more also, if Adonijah have not spoken this word against his own life.
Then King Solomon swore by the LORD, saying, "God do so to me and more also if this word does not cost Adonijah his life!
Then King Solomon made a vow before the LORD : “May God strike me and even kill me if Adonijah has not sealed his fate with this request.