Martin Luther-

Martin Luther on how to teach and comfort struggling Christians who are afflicted by their sin:

"We, on the other hand, teach and comfort an afflicted sinner this way: “Brother, it is impossible for you to become so righteous in this life that your body is as clear and spotless as the sun. You still have spots and wrinkles (Eph. 5:27), and yet you are holy.” But you say: “How can I be holy when I have sin and am aware of it?” “That you feel and acknowledge sin—this is good. Thank God, and do not despair. It is one step toward health when a sick man admits and confesses his disease.” “But how will I be liberated from sin?” “Run to Christ, the Physician, who heals the contrite of heart and saves sinners. Believe in Him. If you believe, you are righteous, because you attribute to God the glory of being almighty, merciful, truthful, etc. You justify and praise God. In short, you attribute divinity and everything to Him. And the sin that still remains in you is not imputed but is forgiven for the sake of Christ, in whom you believe and who is perfectly righteous in a formal sense. His righteousness is yours; your sin is His.”

~Luther’s Works, Lectures on Galatians, 1535: 26:233