Some more on holiness in connection with the one, holy, catholic and apostolic church . . .
"Forgiveness is needed constantly, for although God's grace has been won by Christ, and holiness has been wrought by the Holy Spirit through God's Word in the unity of the Christian church, yet because we are encumbered with our flesh we are never without sin.
"Therefore everything in the Christian church is so ordered that we may daily obtain full forgiveness of sins through the Word and through signs appointed to comfort and revive our consciences as long as we live. Although we have sin, the Holy Spirit sees to it that it does not harm us because we are in the Christian church, where there is full forgiveness of sin. God forgives us, and we forgive, bear with, and aid one another.
"But outside the Christian church (that is, where the Gospel is not) there is no forgiveness, and hence no holiness."
(Large Catechism, The Third Article, 54-56)
"Our churches also teach that one holy church is to continue forever."
(Confessio Augustana, Article VII)