Jesus continues to spiral into a very short and direct statement of the gospel itself. I'll follow suit.
19 And no unclean thing can enter into his kingdom; therefore nothing entereth into his rest save it be those who have washed their garments in my blood, because of their faith, and the repentance of all their sins, and their faithfulness unto the end.
I know there are many ideas of what "salvation" is. Christ puts it in a very stark light - salvation is to be clean and in God's kingdom. So much for disputations on what salvation is.
Then, we are told that we are only saved through being clean through Jesus' blood or his atonement for us. He cleans us and makes us fit for God's kingdom. He does it "because" of faith in Christ, "repentance of all their sins", and faithfulness until death. Christ has specific qualifications for the cleansing he can do and they are all actions or works that must be done.
Doing these things does not cleanse us. Christ cleans us. However, Jesus won't clean us for entering the kingdom of God unless he sees our individual effort on the requirements he has spoken in this short verse.
This is very clear and very specific. Put your trust in Christ and what he can do, become obedient to his commandments, and keep doing all of this and following his example for as long as you live. As you do this, Jesus cleans you and brings you to the rest of God's kingdom. It is simple and easy to understand, yet challenging to do.