Be appeased, O Lord, by our humble prayers, and in Your kindness assist this institution of marriage which You have ordained for the propagation of the human race; so that this union made here, joined by Your authority, may be preserved by Your help. Through the same our Lord Jesus Christ, Your Son, Who lives and reigns with You in the unity of the Holy Spirit, God, world without end. Amen.
Further reading
The shorter blessing asks God to preserve the union begun in marriage. The Little Oratory, by David Clayton and Leila Marie Lawler, offers practical ways for a household to make shared prayer part of everyday life.