Maximus, Sermon III. p. 538, on Modesty and Chastity. Also, John of Damascus, Book III.— Parallel Chap. 27.
It is not only fornication, but also the giving in marriage prematurely, that is called fornication; when, so to speak, one not of ripe age is given to a husband, either of her own accord or by her parents.
Source: Fragments (New Advent)