24. Lo, how the dragon’s tail of the devil and all hell must follow unbelief!
The reason is, that he who does not believe in Christ, has already turned away from God and quite separated himself from him. Therefore he cannot have the Holy Spirit, nor originate good thoughts, nor have a true, hearty pleasure in living according to God’s will; notwithstanding he may outwardly assume a different appearance, like a hypocrite, and act so as not to be rebuked or chastised. Just like a bad, ill-behaved servant, who is inimical to his master, and does what he hates to do, only because he is compelled, and as opportunity arises, does evil. Such are the beautiful, precious fruits, produced by this fountain and stem, if Christ is not accepted and heard as the Savior, presented to us by God in order to blot out our sin and to take from us God’s wrath.
Cantate - Third Sermon - Luther's Sermons, Lenker edition
10. Again, Christ says: “He that disbelieveth,” even though he be baptized, “shall be damned.” These words, too, you must allow to remain just as they are. For he does not say thus: He that disbelieves and does evil works besides; but, without any varnish he says: If thou hadst the chastity of all virgins, the sufferings of all martyrs, and, to be concise, if thou hadst all the works that ever were done by all the saints — if thou hadst all these in a heap, yet, if faith were lacking, all would be lost.
Ascension Sermon, Vol 3, Luther's Sermons