Immediately upon His coming out of the water, Jesus was confirmed when the Holy Spirit descended upon Him in the form of a dove and the Father's voice was heard saying, “This is my beloved Son, with whom I am well pleased.” St. Irenaeus of Lyons wrote: "...in the name of Christ is understood he who anoints, he who has been anointed, and the anointing itself by which he has been anointed: He who anoints is the Father, he who has been anointed is the Son, and he has been anointed in the Spirit, who is the anointing" (Adv. Haer, III,18,3). What is confirmed in this Trinitarian theophany is Jesus' identity as the Only Begotten Son of the Father.
Our reading today from the Acts of the Apostles is a key passage for understanding the universality of the salvation Jesus Christ, still now, seeks to give. Of course, both our Gospel passage and reading from Acts can be seen as the fulfillment (Matthew's account of the Lord's baptism) and realization (Peter baptizing the household of the Roman Cornelius) of what Isaiah prophesied.
In an effort to demonstrate the reciprocal relationship between Advent and Christmas (always summarized well for me in the words of my favorite Christmas carol, "Oh Holy Night"- "Long lay the world in sin and error pining/Till he appear'd and the soul felt its worth/A thrill of hope the weary world rejoices/For yonder breaks a new and glorious morn!"), the realization of the fulfillment of God's plan in, through, and by Jesus Christ will continue until the Lord's glorious return.
It bears noting once again that Baptism is the fundamental sacrament of the Christian life, not the conferral of the sacrament of orders, as many seem these days to suppose. The Sacraments of Initiation remain Baptism, Confirmation, Eucharist (in that order, I might add, getting them out of order has caused a lot of confusion). Hence, the Sacrament of Orders does not complete Christian initiation, receiving Holy Communion does.
So, we live our Baptism, thus seeking make our very lives sacraments, that is, visible and tangible signs of Christ's presence in and for the world.
Springs of water were made holy as Christ revealed his glory to the world. Draw water from the fountain of the Savior, for Christ our God has hallowed all creation (Antiphon 2 for Morning Prayer for today's Feast)