"Whoever claims to live in him must live as Jesus did." (1 John 2:6)
If anyone sins, we have an advocate with the Father, Jesus Christ the Righteous One. He is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world. We know that we have come to know him if we keep his commands. Whoever says I know him but does not do what he commands is a liar and the truth is not in that person. But if anyone obeys his word, love for God is truly made complete in them. This is how we know we are in him: Whoever claims to live in him must live as Jesus did. The Catechism identifies this as the foundational principle of Christian moral theology: the ethical life is not primarily a set of rules but the imitation of Christ, living as he lived (CCC 520).
The command to love one another is both old, going back to the beginning, and new, because the darkness is passing and the true light is already shining. Whoever claims to be in the light but hates a brother or sister is still in the darkness. Whoever loves their brother and sister lives in the light and there is nothing in them to make them stumble. Do not love the world or anything in the world. If anyone loves the world, love for the Father is not in them. For everything in the world, the lust of the flesh, the lust of the eyes, and the pride of life, comes not from the Father but from the world. The world and its desires pass away, but whoever does the will of God lives forever. As for those who have heard that antichrist is coming: there are already many antichrists, anyone who denies that Jesus is the Christ.
Brothers and sisters, whoever claims to live in him must live as Jesus did. This is the test that John applies to every spiritual claim. Not: do you have powerful experiences? Not: do you hold correct doctrine? But: do you live as Jesus lived? In humility, in service, in love for the one in front of you, in obedience to the Father. The claim to know him must be matched by the life that shows it.
Lord Jesus, our advocate with the Father, atoning sacrifice for our sins and for the sins of the whole world: let us live as you lived. Give us the obedience that loves your commands and the love for our brothers and sisters that walks in the light. Through Christ our Lord. Amen.