From this you may perceive the foundation of the true doctrine, from which you should not deviate in the least. Note well that the true doctrine points you to Christ and presents Him, in order that you may be truly comforted against sin and death. This is done by teaching that we should believe Christ to be true, eternal and almighty God, one with the Father and the Holy Ghost, who has come to us on earth, conceived by the Holy Ghost and born of the Virgin Mary. He finally died on the cross, not for His own sins, but for our sins; in order that God might be reconciled and our debt might be canceled, and that we might arise from the dead and come to the enjoyment of everlasting life. In our behalf, Christ has conquered sin and death, so that these no more can harm us; now Christ sitteth at the right hand of God, protecting us against the devil, bestowing upon us the gifts of the Holy Ghost, and answering all our prayer, offered in His name for all we need for body and soul. This is the true doctrine concerning Christ and agrees throughout with the Word, which alone will enable us to resist Antichrist and his lies.

(Luther’s House Postil, Sermon for the Twenty-Fifth Sunday after Trinity, Volume 3, p. 900-901)

Therefore we are indeed unhappy people, because we are so well provided with the Word of God and yet are so very slow to believe. This is the fault of the devil and of our shameful old Adam. For if we had an earnest desire for righteousness and salvation and all that we need, we would believe in the Lord Jesus and hope for everything through Him. For faith, as you have heard, can never be put to shame. Therefore the Lord extols faith very highly, saying: “Thy faith hath made thee whole.” The same faith in Christ will also help us, raise us from death unto life, conquer the devil, dispel our sins, and give us eternal life; all of which, though it is done by Christ, is nevertheless ascribed to faith. For it can never be obtained without faith. Even Christ, the holy sacraments, and the Word of God, or the preaching of the Gospel, cannot help or benefit us without faith. Faith must do it, else it will never be done. So much concerning the first miracle. (Luther’s House Postil, Sermon for the Twenty-Fourth Sunday after Trinity, Volume 3, p. 884-885)