The Catechism of the Summa - Tertia Pars - XXVI. OF THOSE WHO CAN RECEIVE THE SACRAMENT OF BAPTISM; AND OF ITS NECESSITY FOR ALL (A)

(A) Are all men bound to receive Baptism?

Yes, they are absolutely bound to receive Baptism; for if an adult is able to receive it and yet does not, through his own fault, he cannot be saved. The reason is because by Baptism we are incorporated with Jesus Christ; but since Adam's sin no man can be saved unless he be incorporated with Jesus Christ (LXVIII. 1-2).

But do not faith and charity suffice to be incorporated with Jesus Christ by grace in order to be saved?

Without doubt, except that faith cannot be sincere, and charity or grace cannot be in the soul if a man separate them from Baptism through his own fault, for Baptism is the sacrament of faith and produces the first grace in the soul which unites us to Jesus Christ (LXVIII. 2).

Can then one receive Baptism in the state of sin, whether it be question of original sin which is the case for all or of personal grave sins in addition?

Yes; and for this reason Baptism is called the sacrament of the dead, for it does not presuppose grace in the soul as do the sacraments of the living; indeed its proper effect is to give the life of grace to those who have it not. If, however, it be question of adults who have committed mortal sins, in order for them to receive Baptism with fruit, they should renounce all affection for sin (LXVIII. 4).

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