There are no sinners in Christ Jesus, in whom is no sinning. No matter what religion they hail from.
Paul wrote, Romans 7:15-20 (WEB):
(15) For I don’t know what I am doing. For I don’t practice what I desire to do; but what I hate, that I do.
(16) But if what I don’t desire, that I do, I consent to the law that it is good.
(17) So now it is no more I that do it, but sin which dwells in me.
(18) For I know that in me, that is, in my flesh, dwells no good thing. For desire is present with me, but I don’t find it doing that which is good.
(19) For the good which I desire, I don’t do; but the evil which I don’t desire, that I practice.
(20) But if what I don’t desire, that I do, it is no more I that do it, but sin which dwells in me.
So Paul admits that even he still sinned. None of us are perfect now, because, as Paul explains, we are still living in our human bodies which have a sinful nature - sin dwells in us. We consent that God's Law is good and that some of our actions are contrary to it, but Paul attributes the sin to the sinful nature of our human bodies and not to the will of the new man that we are becoming (being transformed into):
Ephesians 4:17-24 (WEB):
(17) This I say therefore, and testify in the Lord, that you no longer walk as the rest of the Gentiles also walk, in the futility of their mind,
(18) being darkened in their understanding, alienated from the life of God, because of the ignorance that is in them, because of the hardening of their hearts;
(19) who having become callous gave themselves up to lust, to work all uncleanness with greediness.
(20) But you didn’t learn Christ that way;
(21) if indeed you heard him, and were taught in him, even as truth is in Jesus:
(22) that you put away, as concerning your former way of life, the old man, that grows corrupt after the lusts of deceit;
(23) and that you be renewed in the spirit of your mind,
(24) and put on the new man, who in the likeness of God has been created in righteousness and holiness of truth.
2 Corinthians 4:16 (WEB):
(16) Therefore we don’t faint, but though our outward man is decaying, yet our inward man is renewed day by day.
or (ESV):
(16) So we do not lose heart. Though our outer self is wasting away, our inner self is being renewed day by day.
1 John 2:1 (MKJV):
(1) My little children, I write these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous.
Jesus taught us to pray for forgiveness for our sins (Luke 11:4), and John wrote, 1 John 1:8-10 (WEB):
(8) If we say that we have no sin, we deceive ourselves, and the truth is not in us.
(9) If we confess our sins, he is faithful and righteous to forgive us the sins, and to cleanse us from all unrighteousness.
(10) If we say that we haven’t sinned, we make him a liar, and his word is not in us.