From a homily at a Mass for families in 1986:
To wed, for two Christians, is first and foremost an act of faith; it is a way to transfer their human love into the supernatural order, it is an entrusting of their love to God, so that God himself will take it into his care, guaranteeing it with his grace and his benediction.
According to the very words of the divine Master, it is not so much that they are joining together, but rather that our Heavenly Father is joining them. And their principal duty will be to not break this union. They will succeed to the degree that they remember that God himself is the guarantor of this union and that therefore, in the difficult moments, they can turn to him with full and limitless faith.