John Gill Commentary 1 Kings 2:23

"Then king Solomon sware by Jehovah, saying, God do so to me, and more also, if Adonijah hath not spoken this word against his own life." — 1 Kings 2:23 (ASV)

Then King Solomon sware by the Lord
To prevent his mother pressing him to have her petition granted:

saying, God do so to me, and more also ;
lay such and such evils upon me, and more than I care to express:

if Adonijah have not spoken this word against his own life ;
to his own prejudice, and even to the loss of his life; in which Solomon suggests it would issue, being a fresh overt act of treason;

he knew, from what Bathsheba said, that this was his petition, and that he had spoken of this to her, and put her upon making it for him;

and who no doubt related to Solomon the whole of the conversation that passed between them, and to which he seems to have some respect in his answer.