Dear friend, in your Baptism you entered into brotherhood with Christ, with all the angels, saints, and Christians on earth. Hold to this fraternity, and live up to its demands, and you have brotherhoods enough. - Luther

Christianity is nothing but the constant practicing of this passage, namely, being convinced that you have no sin although you have sinned, that your sins rest on Christ, who is the eternal Savior from sin, death and hell. - M. Luther

"The promises of God give what the commands of God ask, and fulfill what the law prescribes, that all things may be of God alone, both the commands and the fulfilling of the commands. He alone commands, He also alone fulfills." - Martin Luther, On Christian Liberty
The article of justification must be sounded in our ears incessantly because the frailty of our flesh will not permit us to take hold of it perfectly and to believe it with all our heart.” ― Martin Luther, Commentary on Galatians