If you have ever doubted your salvation due to your sin, this quote from Charles Spurgeon will provide comfort.
I know what the devil will say to you. He will say to you, ‘You are a sinner!’ Tell him you know you are, but that for all that you are justified. He will tell you of the greatness of your sin. Tell him of the greatness of Christ’s righteousness. He will tell you of all your mishaps and your backslidings, of your offences and your wanderings. Tell him, and tell your own conscience, that you know all that, but that Jesus Christ came to save sinners, and that, although your sin be great, Christ is quite able to put it all away.
Some of you, it seems to me, do not trust in Christ as sinners. You get a mingle-mangle kind of faith. You trust in Christ as though you thought Christ could do something for you, and you could do the rest. I tell you that while you look to yourselves, you do not know what faith means. You must be convinced that there is nothing good in yourselves; you must know that you are sinners, and that in your hearts you are as big and as black sinners as the very worst and vilest, and that you must come to Jesus, and leave our fancied righteousnesses, and your pretended goodnesses behind you, and you must take him for everything and trust in him.
Oh! To feel your sin, and yet to know your righteousnesses—o have the two together—repentance on account of sin, and yet a glorious confidence in the all-atoning sacrifice!
—This excerpt comes from the sermon entitled, “Justification by Faith” based on Romans 5:1 which says, “Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ.”