So Bathsheba went to the king to speak to him on behalf of Adonijah. The king stood up to greet his mother and bowed to her. Then he sat on his throne and had another one brought in on which she sat at his right.
She said, "I have a small favor to ask of you; please do not refuse me." "What is it, mother?" he asked. "I will not refuse you."
She answered, "Let your brother Adonijah have Abishag as his wife."
"Why do you ask me to give Abishag to him?" the king asked. "You might as well ask me to give him the throne too. After all, he is my older brother, and Abiathar the priest and Joab are on his side!"
References for 1 Kings 2:22
Then Solomon made a solemn promise in the Lord's name, "May God strike me dead if I don't make Adonijah pay with his life for asking this!
The Lord has firmly established me on the throne of my father David; he has kept his promise and given the kingdom to me and my descendants. I swear by the living Lord that Adonijah will die this very day!"
So King Solomon gave orders to Benaiah, who went out and killed Adonijah.