From: Mark 1:7-11
The Ministry of John the Baptist
 And he (John the Baptist) preached, saying, "After me comes he who
is mightier than I, the thong of whose sandals I am not worthy to stoop
down and untie.  I have baptized you with water, but he will baptize
you with the Holy Spirit."
Jesus Is Baptized
 In those days Jesus came from Nazareth of Galilee and was baptized
by John in the Jordan.  And when he came up out of the water,
immediately he saw the heavens opened and the Spirit descending upon
him like a dove;  and a voice came from heaven, "Thou art my beloved
Son; with thee I am well pleased."
8. "Baptizing with the Holy Spirit" refers to the Baptism Jesus will
institute and shows how it differs from the baptism of John. In John's
baptism, as in the other rites of the Old Testament, grace was only
signified, symbolized. "By the baptism of the New Law, men are
baptized inwardly by the Holy Spirit, and this is accomplished by God
alone. But by the baptism of John the body alone was cleansed by the
water" (St. Thomas Aquinas, "Summa Theologiae, III, q. 38, art. 2 ad
1). In Christian Baptism, instituted by our Lord, the baptismal rite
not only signifies grace but is the effective cause of grace, i.e. it
confers grace. "Baptism confers the first sanctifying grace and the
supernatural virtues, taking away Original Sin and also personal sins
if there are any, together with the entire debt of punishment which the
baptized person owes for sin. In addition, Baptism impresses the
Christian character in the soul and makes it able to receive the other
sacraments" ("St. Pius X Catechism", 295). The effects of Christian
Baptism, like everything to do with the sanctification of souls, are
attributed to the Holy Spirit, the "Sanctifier". It should be pointed
out, however, that like all the "ad extra" actions of God (i.e. actions
external to the intimate life of the Blessed Trinity), the
sanctification of souls is the work of all three Divine Persons.
9. Our Lord's hidden life takes place (apart form his birth at Bethlehem
and the time he was in Egypt) in Nazareth of Galilee from where he comes
to receive John's baptism.
Jesus has no need to receive this baptism of conversion. However, it
was appropriate that he who was going to establish the New Alliance
should recognize and accept the mission of his Precursor by being
baptized with his baptism: this would encourage people to prepare to
receive the Baptism which WAS necessary. The Fathers comment that our
Lord went to receive John's baptism in order to fulfill all
righteousness (cf. Mt 3:15), to give us an example of humility, to
become widely known, to have people believe in Him and to give
life-giving strength to the waters of Baptism.
"Ever since the Baptism of Christ in the water, Baptism removes the sins
of all" (St Augustine, "Sermon" 135).
"There are two different periods of time which relate to Baptism--one
the period of its institution by the Redeemer; the other the
establishment of the law regarding its reception. [...] The second
period to be distinguished, that is, the time when the law of Baptism
was made, also admits of no doubt. Holy writers are unanimous in
saying that after the Resurrection of our Lord, when he gave to his
Apostles the command to go and 'make disciples of all nations,
baptizing them in the name of the Father and of the Son and of the Holy
Ghost' (Mt 28:19) the law of Baptism became obligatory on all who were
to be saved" ("St. Pius V Catechism", Part II).
10. The visible presence of the Holy Spirit in the form of a dove marks
the beginning of Christ's public ministry. The Holy Spirit will also
appear, in the form of tongues of fire, on the occasion when the Church
begins its mission to all the world on the day of Pentecost (cf. Acts
The Fathers usually interpret the dove as a symbol of peace and
reconciliation between God and men. It first appears in the account of
the flood (Gen 8:10-11) as a sign that God's punishment of mankind has
come to an end. Its presence at the beginning of Christ's public
ministry symbolizes the peace and reconciliation he will bring.
11. At the very beginning of his public life the mystery of the Holy
Trinity is made manifest: "The Son is baptized, the Holy Spirit descends
in the form of a dove and the voice of the Father is heard" (St Bede,
"In Marci Evangelium expositio, in loc."). "The Holy Spirit dwells in
him," the same author goes on, "but not from the moment of his Baptism,
but from the moment he became man." In other words, Jesus did not
become God's son at his Baptism; he is the Son of God from all eternity.
Nor did he become the Messiah at this point; he was the Messiah from the
moment he became man.
Baptism is the public manifestation of Jesus as Son of God and as
Messiah, ratified by the presence of the Blessed Trinity.
"The Holy Spirit descended visibly in bodily form upon Christ when he
was baptized so that we may believe him to descend invisibly upon all
those who are baptized afterwards" (St Thomas Aquinas, "Summa
Theologiae", III, q. 39, a. 6 and 3).
Source: "The Navarre Bible: Text and Commentaries". Biblical text
taken from the Revised Standard Version and New Vulgate. Commentaries
made by members of the Faculty of Theology of the University of
Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock,
Co. Dublin, Ireland.