1 Kings 2:22-23

22But King Solomon said to his mother, ‘You are asking me to give Abishag to Adonijah as his wife! You should also ask me to give my kingdom to him, my older brother! That would be the same thing. Then he would rule together with Abiathar the priest and Zeruiah's son Joab!’

23Then King Solomon made this strong promise in the Lord's name. He said, ‘Because Adonijah has asked to have Abishag as his wife, I will certainly punish him with death. If I do not do that, I pray that God will punish me instead!