What is the first thing Jesus says to us when we enter his school? Answer: Ephesians 4 verses 22–24 (my literal translation):
Put off the old person [or: old self; or: old man] which accords with the former way of life and which is corrupted in accord with the desires of deceit. And be renewed in the spirit of your mind. And put on the new person which was created in accordance with God in righteousness and holiness of the truth.
And so after you hear the voice of Christ and are made alive and brought to faith in him and enter into his school to let him teach you how to live, the first thing he says to you is: "change your clothes." Take off the old person and put on the new person.
Read or listen to the entire sermon, "Put on the New Person" (1986).