31 Let all bitterness and wrath and anger and clamor and slander be put away from you, along with all malice. 32 Be kind to one another, tenderhearted, forgiving one another, as God in Christ forgave you.
In chapters 1 through 3 of Ephesians Paul outlined, explained, and expanded the gospel for us, but the gospel does not leave us unchanged. The gospel is transformative, but we are not transformed by focusing on the fruit of the gospel, but the root of the gospel. When we want to improve the fruit production of an apple tree we don’t put our attention on the apples already on the tree, instead we focus on the root of the tree making sure it gets the water and the nutrients it needs to produce more apples. So when Paul tells us to put away our sinfulness like bitterness, wrath, anger and slander and to be kind, tenderhearted and forgiving we don’t become less sinful and more righteous by focusing on becoming less sinful and more righteous, we become that way by looking to Christ and what he has already accomplished for us through this death and resurrection. That’s why Paul says that we are to forgive, because God in Christ forgave us. Our underserved forgiveness is why we forgive. So then the gospel is what transforms us as we look into the face of our wonderful savior Jesus Christ.