Baptism...

Excerpts from the Commentary of Ursinus on the Heidelberg Catechism Q.67 and Q. 70:

Baptism is a sacred rite instituted by Christ in the New Testament, by which we are washed with water in the name of the Father, and of the Son, and of the Holy Ghost, to signify that God receives us into his favor, on account of the blood which his Son shed for us, and that we are regenerated by his Spirit ; and that we, on the other hand, bind ourselves to exercise faith in God, and to perform new obedience to him...

There is in baptism a double washing: an external washing with water, and an internal washing with the blood and Spirit of Christ. The internal is signified and sealed by that which is external, and is always joined with it in the proper use of baptism. This internal washing is again two-fold, being a washing with the blood and Spirit of Christ. Both are specified in the answer of the Catechism, and may take place at the same time. To be washed with the blood of Christ, is to receive the pardon of sin, or to be justified on account of his shed-blood. To be washed with the Spirit of Christ, is to be regenerated by the Holy Spirit, which consists in a change of evil inclinations into those which are good, which the Holy Ghost works in the will and heart, so as to produce in us hatred to sin, and a desire to live according to the will of God...

Baptism is, therefore, the sign of both these forms of washing, or benefits of Christ, which include the forgiveness of sin, and the renewing of our nature ; and that not only because it has some resemblance to both, but also because these two benefits are inseparably connected, so that neither one can be without the other. If Christ do not wash us we have no part in him, and he who has not the Spirit of Christ is none of his. These benefits, however, differ from each other. Justification, which is by the blood of Christ, is complete and perfect in this life by imputation, for " there is no condemnation to them which are in Christ Jesus." (Rom. 8:1.) Regeneration, on the other hand, which is effected by the Spirit of Christ, and which consists in a change of our evil nature to that which is good, is not perfected, but only begun in this life ; yet in such a manner that this beginning does really take place in all the godly, and is experienced by them as long as they are in this life, because they truly and heartily desire to obey God in all things, and are greatly grieved on account of their defects, and remaining corruption...

He that believeth: The condition of faith is joined to the promise ; for those who are baptized do not receive that which is promised and sealed by baptism unless they have faith, so that without faith the promise is not ratified, and baptism is of no profit. In these words we have expressed in a concise manner the proper use of baptism, in which the sacraments are always ratified to those who receive them in faith ; whilst the sacraments are no sacraments, and profit nothing in their improper use...

Shall be saved, that is, he that is baptized may know that he enjoys the benefits which are signified by this sacrament, which consist in justification, and regeneration if he believe. For the promise is not ratified without faith, neither is baptism of any profit when thus received. The promise of salvation is added both to faith and baptism, but in a different respect. It is added to faith, as the necessary means by which we receive salvation ; and to baptism, as the sign which seals that which faith receives.