Lord's Day 27

Q. 72.  Is then the external baptism with water the washing away of sin itself?
A.  Not at all; for the blood of Jesus Christ only, and the Holy Ghost, cleanse us from all sin.1 

Q. 73.  Why then doth the Holy Ghost call baptism “the washing of regeneration,” and “the washing away of sins”?
A.  God speaks thus not without great cause, to wit, not only thereby to teach us that, as the filth of the body is purged away by water, so our sins are removed by the blood and Spirit of Jesus Christ;2 but especially that by this divine pledge and sign He may assure us that we are spiritually cleansed from our sins as really as we are externally washed with water.3 

Q. 74.  Are infants also to be baptized?
A.  Yes; for since they, as well as the adult, are included in the covenant4 and church of God;5 and since redemption from sin by the blood of Christ, and the Holy Ghost, the author of faith, is promised to them6 no less than to the adult; they must therefore by baptism, as a sign of the covenant, be also admitted into the Christian church, and be distinguished from the children of unbelievers7 as was done in the old covenant or testament by circumcision,8 instead of which baptism is instituted in the new covenant.9