The twofold message of the gospel is summed up in the words of Jesus to the woman caught in sin:
(i) I do not condemn you; and (ii) Do not sin any more. (John 8:11).
Justification is the starting line of the Christian race and sanctification is the track on which the race is run. The word 'sanctify' means to be set apart. And so sanctification is the process of being set apart increasingly from sin, the world and our own self-life.
The whole purpose of our coming to Christ is in order that we might be sanctified - just as the whole purpose of an athlete coming to the starting line of a race is to take part in the race. It's pointless an athlete joining others at the starting line if he doesn't intend taking part in the race itself!
Link - https://www.cfcindia.com/books/a-good-foundation