Charles Ellicott Commentary Song Of Solomon 6:9

"My dove, my undefiled, is [but] one; She is the only one of her mother; She is the choice one of her that bare her. The daughters saw her, and called her blessed; [Yea], the queens and the concubines, and they praised her." — Song Of Solomon 6:9 (ASV)

My dove ... is but one. —“While the monarch’s loves are so many, one is mine, my dove, my perfect one: one, the delight of her mother, the darling of her who bore her.” It is impossible not to see in this a eulogy on monogamy, which, in practice, seems always to have been the rule among the Jews, the exceptions lying only with kings and the very rich. The eulogy is made more pronounced by putting an unconscious testimony to the superiority of monogamy into the mouths of the “queens and concubines,” who praise and bless this pattern of a perfect wife.