Adam Clarke on Psalms 45:9

Kings' daughters were among - Applied to Solomon, these words have no difficulty. We know he had seven hundred wives, princesses; and the mention of those here may be intended only to show how highly respected he was among the neighboring sovereigns, when they cheerfully gave him their daughters to constitute his harem. If we apply it to Solomon's marriage with the daughter of the king of Egypt, it may signify no more than the princesses and ladies of honor who accompanied her to the Israelitish court. Applied to Christ, it may signify that the Gospel, though preached particularly to the poor, became also the means of salvation to many of the kings, queens, and nobles, of the earth. The Chaldee interprets the queen standing at his right hand, by the law; and the honorable women, by the different regions and countries coming to receive that law from his right hand. Perhaps by kings' daughters may be meant different regions and countries, which are represented as constituting the families of potentates. Whole nations shall be converted to the Christian faith; and the queen - the Christian Church, shall be most elegantly adorned with all the graces and good works which at once constitute and adorn the Christian character.