"If anyone sees his brother commit a sin that does not lead to death, he should pray and God will give him life. I refer to those whose sin does not lead to death. There is a sin that leads to death. I am not saying that he should pray about that. All wrongdoing is sin, and there is sin that does not lead to death." NIV translation
What is the sin that leads to death? We find the answer in Jesus' words: "But whoever blasphemes against the Holy Spirit will never be forgiven; he is guilty of an eternal sin." This is the only sin that the Lord says cannot be forgiven. The reason is fairly simple, in that, blasphemy of the Holy Spirit is denying its existence and power. In 1 Peter, we learned that it is the Spirit that calls and sanctifies us. Therefore, if the existence of the Spirit is not accepted, it is impossible for the sinner to come to repentance and forgiveness. Without repentance and forgiveness, there is death.
"We know that anyone born of God does not continue to sin; the one who was born of God keeps him safe, and the evil one cannot harm him. We know that we are children of God, and that the whole world is under the control of the evil one." NIV translation
God forgives our sins and if we are truly His children we are not controlled by the sinful nature.
Jesus is the one who protects us and keeps us for eternity. We are His children and not children of the world which is controlled by Satan.
"We know also that the Son of God has come and has given us understanding, so that we may know him who is true. And we are in him who is true - even in his Son Jesus Christ. He is the true God and eternal life. Dear children, keep yourselves from idols." NIV translation
Jesus came and gave us wisdom and a counselor (the Holy Spirit) so that we may understand the things of God. This understanding of the nature of God compels us to stay away from false gods and idolatry.