Original sin (the sin committed by Adam) and all other sins are forgiven and
"washed away" by the waters of baptism. The visible "washing" with water
is a sign of a total, spiritual cleansing.
This teaching is supported first in scripture:
It is through Baptism that we
first die to sin and become "alive for God" (Rom 6:3-4). Thus we read :
"Be baptized every one of you in the name of Jesus Christ, for the remission
of your sins; and you shall receive the Holy Ghost. For the promise is to you
and to your children and to all that are far off, whomsoever the Lord our God
shall call" (Acts 2:38). Later on in the Acts of the Apostles this is again
confirmed with the words "Be baptized, and wash away thy sins" (Acts 22:16).
Even before the Acts of the Apostles, the effect of baptism was prophesised
by Ezechiel - "I will pour upon you clean water, and you shall be cleansed
from all your filthiness".
Then again the Church affirms the teaching that our sins are forgiven in baptism:
In the profession of faith prescribed by Pope Innocent III in 1210 we again
read "We believe that all sins are remitted in baptism, both original sin and
those sins which have been voluntarily committed". The saints and
theologians of the Church profess this teaching also where St Justin Martyr
declares that "in baptism we are created anew, that is, consequently, free
from all stain of sin". St. Ambrose says of baptism: "This is the water in
which the flesh is submerged that all carnal sin may be washed away. Every
transgression is there buried." Tertullian writes: "Baptism
is a carnal act in as much as we are submerged in the water; but the effect
is spiritual, for we are freed from our sins." Finally, the words of
Origen are classic: "If you transgress, you write unto yourself the
handwriting of sin. But, behold, when you have once approached
to the cross of Christ and to the grace of baptism, your handwriting is
affixed to the cross and blotted out in the font of baptism."
It is through the sacraments that God pours forth the supernatural sanctifying
grace needed to become holy and the adopted sons of God conferring the right
to heavenly glory. The grace flows from Christ on the cross with the
sacraments as a channel of that grace.