So what does 1 John 1:5-10 say? (NASB)
5 This is the message we have heard from Him and announce to you, that God is Light, and in Him there is no darkness at all.
6 If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth;
7 but if we walk in the Light as He Himself is in the Light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin.
8 If we say that we have no sin, we are deceiving ourselves and the truth is not in us.
9 If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness. 10 If we say that we have not sinned, we make Him a liar and His word is not in us.
In fact, line 8 and 9 is part of Lutheran Penitential Rite
And continue with 1 John 2
3 By this we know that we have come to know Him, if we keep His commandments.
4 The one who says, “I have come to know Him,” and does not keep His commandments, is a liar, and the truth is not in him;
5 but whoever keeps His word, in him the love of God has truly been perfected. By this we know that we are in Him:
6 the one who says he abides in Him ought himself to walk in the same manner as He walked.
Also, regarding the line, Haydock mentioned thus:
(1Jn5:18). Sinneth not. [See note on 1Jn3:9] — The generation of God preserveth him, (i.e. the grace of adoption, as long as it remains in the soul; see Chap. iii. 9.) and the wicked one (i.e. the devil) toucheth him not. (Witham)
(1Jn3:9) Whosoever abideth in him, complying with his law, sinneth not; and whosoever sinneth, hath not seen him, nor known him; that is, with such a knowledge as is joined with love. (Witham) — Sinneth not; viz. mortally. [See note on 1Jn1:8]
(1Jn1:8) Not that we say or pretend we have no sin; thus truth would not be in us, and we should even make God a liar, who has declared all mankind guilty of sin. We were all born guilty of original sin; we have fallen, and still frequently fall into lesser sins and failings. We can only except from this number our Saviour Christ, who, even as man, never sinned, and his blessed Virgin Mother, by a special privilege, preserved from all kind of sin: and of whom St. Augustine says, “that for the honour of our Lord, when we speak of the holy Virgin Mary, he will have no mention at all made of any sin.” (Witham)