Council of Trent: Session XXIV, Reformation of Marriage, Chapter X

CHAPTER X. The solemnities of marriage are prohibited at certain times.

The holy Synod enjoins, that the ancient prohibitions of solemn nuptials be carefully observed by all, from the Advent of our Lord Jesus Christ until the day of the Epiphany, and from Ash-Wednesday until the octave of Easter inclusively; but at other times It allows marriage to be solemnly celebrated; and the bishops shall take care that they be conducted with becoming modesty and propriety: for marriage is a holy thing, and is to be treated in a holy manner.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).