Whole chapter discussed by Martin Luther —
Jesus Our Advocate
1My little children, I am writing these things to you so that you will not sin. But if anyone does sin, we have an advocate before the Father—Jesus Christ, the Righteous One. 2He Himself is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world.
3By this we can be sure that we have come to know Him: if we keep His commandments. 4If anyone says, “I know Him,” but does not keep His commandments, he is a liar, and the truth is not in him. 5But if anyone keeps His word, the love of God has been truly perfected in him. By this we know that we are in Him: 6Whoever claims to abide in Him must walk as Jesus walked.
A New Commandment
7Beloved, I am not writing to you a new commandment, but an old one, which you have had from the beginning. This commandment is the message you have heard. 8Then again, I am also writing to you a new commandment, which is true in Him and also in you. For the darkness is fading and the true light is already shining.
9If anyone claims to be in the light but hates his brother, he is still in the darkness. 10Whoever loves his brother remains in the light, and there is no cause of stumbling in him. 11But whoever hates his brother is in the darkness and walks in the darkness. He does not know where he is going, because the darkness has blinded his eyes.
12I am writing to you, little children, because your sins have been forgiven through His name.
13I am writing to you, fathers, because you know Him who is from the beginning.
I am writing to you, young men, because you have overcome the evil one.
I have written to you, children, because you know the Father.
14I have written to you, fathers, because you know Him who is from the beginning.
I have written to you, young men, because you are strong, and the word of God abides in you, and you have overcome the evil one.
Do Not Love the World
15Do not love the world or anything in the world. If anyone loves the world, the love of the Father is not in him. 16For all that is in the world—the desires of the flesh, the desires of the eyes, and the pride of life—is not from the Father but from the world. 17The world is passing away, along with its desires; but whoever does the will of God remains forever.
Beware of Antichrists
18Children, it is the last hour; and just as you have heard that the antichrist is coming, so now many antichrists have appeared. This is how we know it is the last hour. 19They went out from us, but they did not belong to us. For if they had belonged to us, they would have remained with us. But their departure made it clear that none of them belonged to us.
20You, however, have an anointing from the Holy One, and all of you know the truth. 21I have not written to you because you lack knowledge of the truth, but because you have it, and because no lie comes from the truth. 22Who is the liar, if it is not the one who denies that Jesus is the Christ? This is the antichrist, who denies the Father and the Son. 23Whoever denies the Son does not have the Father, but whoever confesses the Son has the Father as well.
Remain in Christ
24As for you, let what you have heard from the beginning remain in you. If it does, you will also remain in the Son and in the Father. 25And this is the promise that He Himself made to us: eternal life.
26I have written these things to you about those who are trying to deceive you. 27And as for you, the anointing you received from Him remains in you, and you do not need anyone to teach you. But just as His true and genuine anointing teaches you about all things, so remain in Him as you have been taught.
28And now, little children, remain in Christ, so that when He appears, we may be confident and unashamed before Him at His coming.
29If you know that He is righteous, you also know that everyone who practices righteousness has been born of Him.