55] Thus you see that the objection of the sectarians is vain. For (as we have said) even though infants did not believe, which, however, is not the case, yet their baptism as now shown would be valid, and no one should rebaptize them; just as nothing is detracted from the Sacrament though some one approach it with evil purpose, and he could not be allowed on account of his abuse to take it a second time the selfsame hour, as though he had not received the true Sacrament at first; for that would mean to blaspheme and profane the Sacrament in the worst manner. How dare we think that God’s Word and ordinance should be wrong and invalid because we make a wrong use of it?
56] Therefore I say, if you did not believe then believe now and say thus: The baptism indeed was right, but I, alas! did not receive it aright. For I myself also, and all who are baptized, must speak thus before God: I come hither in my faith and in that of others, yet I cannot rest in this, that I believe, and that many people pray for me; but in this I rest, that it is Thy Word and command. Just as I go to the Sacrament trusting not in my faith, but in the Word of Christ; whether I am strong or weak, that I commit to God. But this I know, that He bids me go, eat and drink, etc., and gives me His body and blood; that will not deceive me or prove false to me.
57] Thus we do also in infant baptism. We bring the child in the conviction and hope that it believes, and we pray that God may grant it faith; but we do not baptize it upon that, but solely upon the command of God. Why so? Because we know that God does not lie. I and my neighbor and, in short, all men, may err and deceive, but the Word of God cannot err.
58] Therefore they are presumptuous, clumsy minds that draw such inferences and conclusions as these: Where there is not the true faith, there also can be no true Baptism. Just as if I would infer: If I do not believe, then Christ is nothing; or thus: If I am not obedient, then father, mother, and government are nothing. Is that a correct conclusion, that whenever any one does not do what he ought, the thing in itself shall be nothing and of no value?
59] My dear, just invert the argument and rather draw this inference: For this very reason Baptism is something and is right, because it has been wrongly received. For if it were not right and true in itself, it could not be misused nor sinned against. The saying is: Abusus non tollit, sed confirmat substantiam, Abuse does not destroy the essence, but confirms it. For gold is not the less gold though a harlot wear it in sin and shame.
60] Therefore let it be decided that Baptism always remains true, retains its full essence, even though a single person should be baptized, and he, in addition, should not believe truly. For God’s ordinance and Word cannot be made variable or be altered by men.
61] But these people, the fanatics, are so blinded that they do not see the Word and command of God, and regard Baptism and the magistrates only as they regard water in the brook or in pots, or as any other man; and because they do not see faith nor obedience, they conclude that they are to be regarded as invalid.
62] Here lurks a concealed seditious devil, who would like to tear the crown from the head of authority and then trample it under foot, and, in addition, pervert and bring to naught all the works and ordinances of God.
63] Therefore we must be watchful and well armed, and not allow ourselves to be directed nor turned away from the Word, in order that we may not regard Baptism as a mere empty sign, as the fanatics dream.
(Martin Luther, The Large Catechism – On Holy Baptism, [IV.55-63], Concordia: The Symbols of the Evangelical Lutheran Church, ed. F. Bente, trans. W. H. T. Dau, St. Louis, 1922.)