Answer
Abishag was a Shunammite woman whose account can be found in 1 Kings 1 and 2. She was connected to King David in a very interesting manner.
As David advanced in years, his health declined. Eventually, whether through declining faculties or an illness, he was unable to keep warm, even when fully clothed. It seems this ailment was a particular problem during the night, so David’s servants devised a plan to keep him warm. They presented their idea to David: “Let us look for a young virgin to serve the king and take care of him. She can lie beside him so that our lord the king may keep warm” (1 Kings 1:2). King David agreed, and, in searching for an exceptionally beautiful woman, they found Abishag.
Abishag, who was a “very beautiful” virgin (1 Kings 1:4), was brought to live at the palace. There she saw to King David’s needs and warmed him with her body at night. The Bible states there was no sexual relationship between the two of them; it was a matter of a caregiver attending her charge (1 Kings 1:4), although it was assumed that Abishag would become a de facto member of David’s harem—a concubine or secondary wife.
Abishag’s story continues after David’s death. David’s son Solomon had been chosen to take the throne, but another of David’s sons, Adonijah, styled himself as king instead (1 Kings 1:5). He was older than Solomon and had plenty of followers, so Adonijah posed a real threat to Solomon’s succession. Even as Adonijah was celebrating his coronation as king, David had Solomon anointed king at Bathsheba’s and Nathan’s request. Hearing the news of his brother’s installation as king, Adonijah was afraid and appealed to Solomon that he be allowed to live in spite of his designs on the throne. Solomon granted him mercy (1 Kings 1:5–53). Unfortunately, Adonijah did not stop scheming for long, and he had his eye on Abishag.
When David passed away and Solomon began his rule, Adonijah approached Bathsheba and requested that she go before King Solomon and ask him to give him Abishag as a wife (1 Kings 2:13–17). She relayed the request, but Solomon saw through Adonijah’s plot. To marry a former king’s wife was to lay claim to the throne, and, since Abishag was considered one of David’s concubines (even though they had never been intimate), Adonijah’s request to marry her was full of intrigue. In short, Adonijah was renewing his bid for Solomon’s throne. This was the last straw, and Solomon ordered that Adonijah be executed immediately (verses 19–25).