CCC 1623 According to Latin tradition, the spouses, as ministers of Christ’s grace, mutually confer upon each other the sacrament of Matrimony by expressing their consent before the Church. In the tradition of the Eastern churches, the priests (bishops or presbyters) are witnesses to the mutual consent of the spouses,¹ but for the validity of the sacrament their blessing is also necessary.²

1 Cf. CCEO, can. 817.
2 Cf. CCEO, can. 828.