פירוש על קידושין 81:11

The Talmud now wants to know how we know that agency works not only in divorce, but also in betrothal. This cannot be derived directly from divorce because divorce differs in that a woman can be divorced against her will. She cannot, however, be married against her will.

The sequence of verbs in the verse about divorce is read as implying that the same means of contracting divorce can be used to contract marriage. Thus just as an agent may be used for divorce, one may be used for marriage.
Note that since the verse implies that marriage and divorce are to be treated the same, this is not considered deriving the rule from divorce, which we stated above cannot be done. Rather, it is a case of simply reading the dictates of the verse.