The Baptism in the Jordan is first of all a mystery of light. Here, as Christ descends into the waters, the innocent one who became “sin” for our sake (cf. 2 Cor 5:21), the heavens open wide and the voice of the Father declares him the beloved Son (cf. Mt 3:17 and parallels), while the Spirit descends on him to invest him with the mission which he is to carry out...
The revelation made directly by the Father at the Baptism in the Jordan and echoed by John the Baptist is placed upon Mary's lips at Cana, and it becomes the great maternal counsel which Mary addresses to the Church of every age: “Do whatever he tells you” (Jn 2:5). This counsel is a fitting introduction to the words and signs of Christ's public ministry and it forms the Marian foundation of all the “mysteries of light”.
Saint John Paul II,
Apostolic Letter Rosarium Virginis Mariae, October 2002, § 21