Why does Solomon act so severely with Adonijah asking for Abishag as his concubine?

CLAIM: Solomon forgave Adonijah for trying to usurp the throne—even when he tried to become king by force. Why then does Solomon have him killed for merely asking for a concubine?

RESPONSE: Solomon already warned Adonijah that his attempt at usurping the throne landed him in hot water. He told him that if he did anything else that he would die: “If he shows himself to be worthy, not a hair of his head will fall to the ground; but if evil is found in him, he will die” (1 Kin. 1:52). Why was taking Abishag so serious?

OPTION #1. The act of taking David’s concubine was a step toward usurping the throne. In ancient times, the king’s harem went to his successor. The Jews (2 Sam. 12:8), the Persians (Herodotus, 3.68), and the Arabs had a similar custom.^[1] This was a not so subtle way of making a move to take over. Since Abishag was part of David’s harem, Solomon saw this as an act of treason.

OPTION #2. Abishag was one of the few witnesses that confirmed David’s choice of Solomon. When David confirmed his promise to Solomon to receive the throne, there was only one other eyewitness: Abishag (1 Kin. 1:15-17). If Adonijah took her as his concubine (and if he could kill Bathsheba), it would be his word versus Solomon’s. If he could force Abishag to confirm his story, he could take over the throne this way. Solomon saw this as an act of treason.

^[1] R. D. Patterson and Hermann J. Austel, “1, 2 Kings,” in The Expositor’s Bible Commentary: 1 & 2 Kings, 1 & 2 Chronicles, Ezra, Nehemiah, Esther, Job, ed. Frank E. Gaebelein, vol. 4 (Grand Rapids, MI: Zondervan Publishing House, 1988), 37.