We have a little sister. — Commentators are almost all at one in the feeling that the poem properly ends with Song of Solomon 8:7. Those who construct the poem on the plan of a drama can find no proper place for what follows (unless as a meaningless epilogue), and the want of cohesion with the main body of the work is so evident that many scholars have rejected it as a later addition; others have tried to find a place for it by re-arranging the whole poem. But if the various sections are, as above explained, only a succession of different presentments of the same story of courtship and marriage, made without any regard to order, but simply as they occurred to the memory of the poet, this conclusion presents no difficulty, either from its position or its meaning. With a view to artistic form, we might wish it away or in some other part of the poem; but the author had no regard to artistic form, or not the same conception of it as we have.
A little sister... — The recollection is carried back to the childhood of the bride. Her brothers are supposed to be debating how to deal with her when an offer of marriage should be made for her.
In the day when she shall be spoken for? — i.e., asked in marriage (comp. 1 Samuel 25:29). At present she is unmarriageable.