I am encouraged by your question because Abishag is not a well-known person in the Bible.  Let’s start reading at the first mention of this young lady.  We read in 1 Kings 1:1-3, “Now king David was old and stricken in years; and they covered him with clothes, but he gat no heat. Wherefore his servants said unto him, Let there be sought for my lord the king a young virgin: and let her stand before the king, and let her cherish him, and let her lie in thy bosom, that my lord the king may get heat. So they sought for a fair damsel throughout all the coasts of Israel, and found Abishag a Shunammite, and brought her to the king.” 

King David, in his advanced years, was failing in his health.  As is the case with many older people with poor blood circulation, he found it difficult to keep warm in his bed, despite wearing his bedclothes.  It was not unusual for people to sleep together for warmth and that is what happened here.  David’s servants sought out a young virgin girl to be a helper for the aging king, and to help him stay warm at night.  They found Abishag, a Shunammite girl.  Shunammite is a term that refers to a person from Shunem, a place in ancient Israel.  Abishag was to “stand before the king, and let her cherish him.”  In other words, she was to “attend the king and become his nurse.” (NASB).  

The fact that she was to be a virgin is probably more to indicate that she was not married and so could give all her time caring for the king.

Now let’s read verse 4 of our chapter. “And the damsel was very fair, and cherished the king, and ministered to him: but the king knew her not.”  The relationship between Abishag and David was purely platonic.  “The king knew her not” is speaking of the fact that he did not know her as a man knows his wife.  This is important to know because later, David’s son, Adonijah, wanted her for himself.  After David’s death, Adonijah asked Bathsheba to speak to King Solomon on his behalf and ask if he could marry her.  “And he said, Speak, I pray thee, unto Solomon the king, (for he will not say thee nay,) that he give me Abishag the Shunammite to wife.” (1 Kings 2:17).   If David had taken Abishag as his wife, it would have been against the Law for Adonijah to have her.  Leviticus 18:8 says, “The nakedness of thy father’s wife shalt thou not uncover: it is thy father’s nakedness.” 

I encourage you to read 1 Kings, chapters 1-2.  It is so informative about Adonijah’s desire to have Abishag.  Adonijah strongly desired to be king and even before his father David’s death, he declared himself to be king, but David had promised that position to Solomon as we read his words to Bathsheba in 1 Kings 1:30, “Even as I sware unto thee by the LORD God of Israel, saying, Assuredly Solomon thy son shall reign after me, and he shall sit upon my throne in my stead; even so will I certainly do this day.”  Upon David’s death, as we just read in 1 Kings 2:17, Adonijah asked to have Abishag.  To Solomon, this indicated that he desired David’s possessions, as his servants would be considered.  This was an act of Adonijah claiming his right to David’s throne.  His request would compromise Solomon’s kingship.  So, that very day, Solomon had Adonijah killed as we read in 1 Kings 2:23-25, “Then king Solomon sware by the LORD, saying, God do so to me, and more also, if Adonijah have not spoken this word against his own life. Now therefore, as the LORD liveth, which hath established me, and set me on the throne of David my father, and who hath made me an house, as he promised, Adonijah shall be put to death this day. And king Solomon sent by the hand of Benaiah the son of Jehoiada; and he fell upon him that he died.” 

This is all we know about Abishag…which is very little.  However, we learn from her story of the privilege of serving our Lord and that there is a true King above all earthly kings, who is sovereign, just, and eternal. We read in Psalm 115:3, “But our God is in the heavens: he hath done whatsoever he hath pleased.”  (CC)  (607.4)