Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

They then looked about for a beautiful girl for this purpose, and found Abishag of Shunem, the present Sulem or Solam, at the south-eastern foot of the Duhy of Little Hermon (see at Jos 19:18), who became the king's nurse and waited upon him. The further remark, "and the king knew her not," is not introduced either to indicate the impotence of David or to show that she did not become David's concubine, but simply to explain how it was that it could possibly occur to Adonijah (Kg1 2:17) to ask for her as his wife. Moreover, the whole affair is to be judged according to the circumstances of the times, when there was nothing offensive in polygamy.