"There are eight sins which militate against faith: 1. Epicurean and Academic doubts about God, His providence and the certainty of the doctrine handed down through Christ and the Apostles. 2. A lack of faith toward God. 3. In regard to the forgiveness of sins, to entertain doubts as to whether we are in the grace of God or if we please God. 4. Despair. 5. Stubbornness of presumption. 6. Confidence in human aids. 7. Superstition. 8. Witchcraft."
David Chytraeus, A Summary of the Christian Faith (1568), Decatur: Repristination Press, 1994. p. 65f.
"The sins which militate against the Third Commandment are the profanation of the Sabbath through neglect and contempt of the ministry, through Judaic and superstitious observance of the Sabbath, or through a shifting of the ministry into the kingdom of this world. The faithfulness of those who teach is the virtue by which the ministers of the Church, aware of their modest skill in Christian doctrine, carefully and zealousy discharge and steadfastly protect all the duties of the faithful dispenser of the mysteries of God in teaching, debating, comforting and setting their hearers an example of true devotion and of all the virtues. The other extreme are faithlessness, heedless teaching or negligence in office, or deserting the ministry because of excessive anxiety or concern over one's own weakness."
Chytraeus, A Summary of the Christian Faith, p. 71f. Chytraeus helped with the Formula and Book of Concord.
"The purest and best part of the human race, the special nursery and flower of God's Church, is tender youth. Youth retains the gift of the Holy Spirit which it received in Baptism; it learns eagerly the true doctrine about God and our Redeemer, Jesus Christ; it calls Him God with a chaste mind and with a simple, pure faith; it thanks Him with a quick and joyful heart for the blessings received from Him; in its studies and the other parts of life, it carries out the duties commanded it; and it obeys God and parents reverently. Particularly God-pleasing, therefore, are the studies of one's earliest age: prayer, obedience and praises which honor God, regardless of how weak and stammering its voice may be."
Chytraeus, A Summary of the Christian Faith, p. 9.
"In this Gospel we see how God distinguishes Christians from heathen. For the Lord does not deliver these teachings to the heathen, for they could not receive them, but to His Christians...Satan also hears the Gospel and the Word of God, yea, he knows it far better than we do, and he could preach it as well as we, if he only wanted to; but the Gospel is a doctrine that should become a living power and be put into practice; it should strengthen and comfort people, and make them courageous and aggressive."
Sermons of Martin Luther, 8 vols., ed. John Nicholas Lenker, Grand Rapids: Baker Book House, 1983, V, p. 103f.
False Doctrine – Relying on Cleverness
"Thesis Seven: Sound Apologetics Can Make Sound Doctrine Sound Good...Logic never converted anyone; but Christianity is logically defensible, once one makes reason ministerial to God and His Word...Read C.S. Lewis, Francis Schaeffer and Josh McDowell for practical apologetic tools. In fact, lend your copy to the prospect whose intelligence and education have become his curse. Once you've read Josh McDowell's 'Lord, Liar, or Lunatic' argument for the deity of Christ, you'll find yourself using it."
Rev. Paul Kelm, "How to Make Sound Doctrine Sound Good to Mission Prospects," p. 14.