23 Then king Solomon sware by Yahweh, saying, Elohim do so to me, and more also, if Adonijah have not spoken this word against his own life.

The Sin of Adonijah

-Adonijah was put to death because Solomon regarded his asking for Abishag as a re-assertion of his claim to the throne. Upon the occasion of his attempted usurpation, Solomon pardoned him on condition that he proved himself a worthy man (1 Sam. 1:5, 52).

He had now evidently lost all faith in him. If Adonijah's object was to re-open his assumed claim to the throne, or to get a footing in the royal house, the better to promote his plans; as Solomon's verdict seems to imply, then he was worthy of death. It was "the word" that Adonijah had spoken through Bathsheba that cost him his life.

The Christadelphian, Mar 1888