We know that no one who is born of God keeps on sinning; the One who was born of God keeps him safe, and the evil one cannot touch him.
In context
16If anyone sees a brother or sister committing a sin that does not lead to death, he should pray, and God will give that person life. This is for anyone whose sin does not lead to death. There is a sin that leads to death; I am not saying he should pray about that. 17All wrongdoing is sin, but there is sin that does not lead to death. 18We know that no one who is born of God keeps on sinning; the One who was born of God keeps him safe, and the evil one cannot touch him. 19We know that we are from God, and that the whole world lies in the power of the evil one. 20And we know 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, in his Son, Jesus Christ. He is the true God and eternal life.