John Gill Bible Commentary

Now therefore, as the Lord liveth,.... Which is another oath; and one may easily perceive hereby in what a temper and disposition Solomon was, how warm, earnest, and vehement, how resolute against the petition, and how determined he was to punish Adonijah and his confederates: which hath established me, and set me upon the throne of David my father, and who hath made me an house, as he promised; who had placed him on his father's throne, and established him there, in spite of all his enemies, and had given him a firm and stable kingdom, which was not to be shaken and subverted by the power and policy of conspirators, according to the promise of God by Nathan, Sa2 7:11; Adonijah shall be put to death this day; both for his former conspiracy, he only having had a reprieve, and which was to continue on his good behaviour, Kg1 1:51, and for his fresh attempt in forming treasonable schemes to ascend the throne if possible; wherefore, being a dangerous man, and no longer to be trusted, Solomon was determined to dispatch him at once, and being established in his kingdom, he had nothing to fear from those in the conspiracy with him.