Q. I am wondering who Solomon’s first wife was. The book of Kings describes how Solomon married the daughter of Pharaoh after making an alliance with Egypt. But the Song of Solomon speaks of his love for the Shulammite.
The Bible does not actually tell us who Solomon’s first wife was. The first woman it describes Solomon marrying was indeed the daughter of Pharaoh, as you say. But that does not necessarily mean she was his first wife.
I think a good case can be made for the argument that his first wife actually was Abishag the Shunammite, presumably the same woman who is called by the similar name Shulammite in the Song of Solomon. This beautiful woman had kept the aging King David warm in his bed when he could no longer stay warm himself, but the Bible is very specific that David did not have sexual relations with her and he was not married to her. This meant that David’s son and successor could marry her. (The Law of Moses forbade a man to marry a woman who had been his father’s wife.)
Solomon’s older half-brother Adonijah, who had tried unsuccessfully to seize the throne for himself even though Solomon was David’s announced choice as successor, recognized that marrying Abishag might still give him some claim to the throne. So he asked Solomon if he could do that. Solomon realized what Adonijah was up to and that it was a violation of Adonijah’s oath not to keep pursuing the throne. Solomon had warned him that he would be put to death if he did that, and when Adonijah make this request, Solomon had him executed.
The Bible says nothing about Abishag after that, but reading between the lines, it makes good sense to think that Solomon then married her himself. As Adonijah had realized, being married to the last woman who had been something like a wife to King David, without actually being his wife, would strengthen his claim to be David’s successor.
But if so, was that all there was to it? Probably not, if Abishag the Shunammite is also the Shulammite of the Song of Solomon. If Solomon was indeed writing about her in that great love poem, then the two of them had much more than a marriage of convenience. It would have been a true love match.
We do need to acknowledge that Solomon later did marry other wives, including Pharaoh’s daughter and the daughters of the kings of many other surrounding nations, for alliance purposes. Ultimately these foreign wives led him to worship idols, and God punished him by taking away most of the kingdom from his successors. So when it came to marriage, unfortunately Solomon did not make very good choices in the end. But we can at least hope that he made a good choice in the beginning, and that for some time he experienced what God intended marriage to be.