22 We can therefore say that in this passage of John's Gospel we find as it were a first manifestation of the truth concerning Mary's maternal care. This truth has also found expression in the teaching of the Second Vatican Council. It is important to note how the Council illustrates Mary's maternal role as it relates to the mediation of Christ. Thus we read: "Mary's maternal function towards mankind in no way obscures or diminishes the unique mediation of Christ, but rather shows its efficacy," because "there is one mediator between God and men, the man Christ Jesus" (1 Tim. 2:5). This maternal role of Mary flows, according to God's good pleasure, "from the superabundance of the merits of Christ; it is founded on his mediation, absolutely depends on it, and draws all its efficacy from it." It is precisely in this sense that the episode at Cana in Galilee offers us a sort of first announcement of Mary's mediation, wholly oriented towards Christ and tending to the revelation of his salvific power. From the text of John it is evident that it is a mediation which is maternal. As the Council proclaims: Mary became "a mother to us in the order of grace." This motherhood in the order of grace flows from her divine motherhood. Because she was, by the design of divine Providence, the mother who nourished the divine Redeemer, Mary became "an associate of unique nobility, and the Lord's humble handmaid," who "cooperated by her obedience, faith, hope and burning charity in the Savior's work of restoring supernatural life to souls." And "this maternity of Mary in the order of grace. . .will last without interruption until the eternal fulfillment of all the elect."
Source: Redemptoris Mater (Vatican.va)