1 John 5:18 “We know that no one who is born of God sins; but He who was born of God keeps him, and the evil one does not touch him.” NASB
What is the meaning of “the evil one does not touch him”?
We must include all available context to understand this correctly. Let's notice v11
And this is the testimony: that God has given to us eternal life...
"has given" This is a case of speaking of that which will be as if it already is. Does anyone have eternal life now? No one except Jesus who is the firstborn of the dead and of creation (same event).
And we see the same approach to the earlier verse 1, with 'has been'.
Everyone believing that Jesus is the Christ has been born of God
We understand from several other passages that being born again refers to the return of Jesus, the first resurrection and transformation of the living saints into ever-living humans. It is at this time that evil will not touch or affect the 'born from above' saints who will rule with Christ on earth.
We know from Rom 6:9 that Jesus was 'mastered by death' while he was in the flesh. Being able to be tempted, he could have sinned and failed in his mission to be the Lamb without blemish.
Now of course, Jesus is master OF death and can no longer sin or be tempted or die. It is in this state that evil will have no effect on the risen, exalted and reborn saints - evil will not touch them and they will never sin again. (2 Cor 5:16 we regard Jesus by the flesh no longer, for he has spirit life 1 Pet 3:18)
We know that everyone having been born of God does not continue to sin... v18
There is no need to twist the scriptures to fit popular theology by changing the words to say, as another answer surmises...
Not that one who is born of God never sins but that one who is born of God is no longer the helpless slave of sin
That is not what John is saying. He says - for good reason, that the reborn person will not sin again. God has not gone to all this trouble to make a new Kingdom which will have the problem of sin again. Jesus has dealt with the problem and for those in the Kingdom, sin will cease.
Certainly, in this age, believers will still sin and may still receive gracious repentance until the day of Jesus' return. But this passage is not talking about this age, but the one to come. If we take the scripture as not contradicting itself when translated and read correctly, this passage affirms the reality of the end of this age and the beginning of the new one explained at length in Rev. and other places.
This is repeated by John in
1 John 3:9 Anyone born of God refuses to practice sin, because God’s seed abides in him; he cannot go on sinning, because he has been born of God.
When resurrected, saints will be filled with the goodness of God and will not sin anymore. Only those who have proved their faith by the lives they live will be granted immortality and they will be like Jesus.
1 John 3:2 we know that when he appears we shall be like him, because we shall see him as he is.