Gerhard and Walther

An upright, repentant person must first of all look to God and, as a result, have remorse and sorrow that with his sin he has offended this most high Good. Also, he must not look at his outward sins, but also at his inward turning away and corruption of his heart and regret it.—Johann Gerhard, Schola Pietatis II:190.

Those who want to belong to the invisible Church have the holy duty to separate themselves from all who falsify God’s Word and obstinately remain in their errors.—C. F. W. Walther, God Grant It!, p. 380.