Even if he would, he could not lose his salvation, however much he sinned, unless he refused to believe. For no sin can condemn him save unbelief alone. All other sins, so long as the faith in God’s promise made in baptism returns or remains, are immediately blotted out through that same faith, or rather through the truth of God, because he cannot deny himself if you confess him and faithfully cling to him in his promise. But as for contrition, confession of sins, and satisfaction, along with all those carefully devised exercises of men: if you rely on them and neglect this truth of God, they will suddenly fail you and leave you more wretched than before. For whatever is clone without faith in God’s truth is vanity of vanities and vexation of spirit [Eccles. 1:2, 14]" [LW 36: 60].An interesting historical analysis of this quote can be found here. A Lutheran recently left a portion of this quote in the comment section under the same entry stating,
Having graduated from a Lutheran seminary, this is the position of the Lutheran Church. It is different than Wesleyism in the sense that it does not teach that one loses their salvation because of sin, but that sin may have such an effect on a person that one may lose their faith, thus, coming to a place of unbelief!I'm bringing this up simply to point out a significant difference between Luther and Reformed theology that is often overlooked from the Reformed side. Note the following difference between Luther's quote, the Lutheran comment, and the following from R.C. Sproul. Note how Sproul connects the sin of unbelief to limited atonement:
However, the overwhelming majority of Christians who reject limited atonement also reject universal salvation. They are particularists, not universalists. They insist on the doctrine of justification by faith alone. That is, only believers are saved by the atonement of Christ. If that is so, then the atonement, in some sense, must be limited, or restricted, to a definite group, namely believers. If Christ died for all of the sins of all people, that must include the sin of unbelief. If God’s justice is totally satisfied by Christ’s work on the cross, then it would follow that God would be unjust in punishing the unrepentant sinner for his unbelief and impenitence because those sins were already paid for by Christ.See also, this comment from Dr. Sproul. This is popular Reformed argumentation. Note A.W. Pink's construction of it:
If ALL the sins of ALL men were laid upon Christ, then the sin of unbelief was too. That unbelief is a sin is clear from the fact that in 1 John 3:23 we read, "And this is His commandment, That we should believe on the name of His Son Jesus Christ." Refusal to believe in Christ is, therefore, an act of flagrant disobedience, rebellion against the Most High. But if all the sins of all men were laid upon Christ (as it is now asserted), then He also endured the penalty for the Christ-rejector's unbelief. If this be so, then Universalism is true. But it is not so. The very advocates of the view we are now refuting would not affirm it. And therein may be seen the inconsistency and untenableness of their teaching. For if unbelief is a sin and Christ did not suffer the penalty of it, then all sin was not laid upon Christ. Thus there are only two alternatives: a strictly limited Atonement, availing only for believers; or an unlimited Atonement which effectually secures the salvation of the entire human race.See also John Owen's construction of the argument.
So, the moral of this story is that Calvinists should careful with Luther, and also be prepared for a long and tedious discussions with Lutherans on the extent of the atonement, and the meaning of the atonement.