These things I have written to you who believe in the name of the Son of God, that you may know that you have eternal life, and that you may continue to believe in the name of the Son of God. (1 John 5:13)
We must take good account of “these things,” the two words with which 1 John 5:13 begins because it is by means of them that John seeks to offer assurance about eternal life to those who believe on the Lord Jesus Christ. There is a context that precedes, and “these things” connects us to that. The phrase, “that you may know,” is a purpose clause that connects us back to “these things,” which in turn connects us back to the preceding context.
What, then, are the “these things” of which John is speaking? They are the things John has written about in his letter up to this point — from 1 John 1:1 all the way up to 5:12. What are the things he wrote about? For one thing, he wrote about light, and walking in the light: “If we say that we have fellowship with Him, and walk in darkness, we lie and do not practice the truth. But if we walk in the light as He is in the light, we have fellowship with one another, and the blood of Jesus Christ His Son cleanses us from all sin” (1 John 1:6-7).
He wrote about not loving the world: “Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world — the lust of the flesh, the lust of the eyes, and the pride of life — is not of the Father but is of the world” (1 John 2:15-16).
He wrote about a lifestyle of righteousness: “In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God …” (1 John 3:10). Along with that, he wrote about the imperative of loving one another, not only in word but also in deed: “... nor is he who does not love his brother. For this is the message that you heard from the beginning, that we should love one another” (1 John 3:10-11). He continues on this theme of love quite extensively:
Whoever hates his brother is a murderer, and you know that no murderer has eternal life abiding in him. By this we know love, because He laid down His life for us. And we also ought to lay down our lives for the brethren. But whoever has this world’s goods, and sees his brother in need, and shuts up his heart from him, how does the love of God abide in him?He also writes about faith in Christ — it is one of the two commandments John says that God has given us:
My little children, let us not love in word or in tongue, but in deed and in truth. And by this we know that we are of the truth, and shall assure our hearts before Him. For if our heart condemns us, God is greater than our heart, and knows all things.
Beloved, if our heart does not condemn us, we have confidence toward God. And whatever we ask we receive from Him, because we keep His commandments and do those things that are pleasing in His sight. And this is His commandment: that we should believe on the name of His Son Jesus Christ and love one another, as He gave us commandment. Now he who keeps His commandments abides in Him, and He in him. And by this we know that He abides in us, by the Spirit whom He has given us (1 John 3:15-24)
“Beloved, let us love one another, for love is of God; and everyone who loves is born of God and knows God. He who does not love does not know God, for God is love” (1 John 4:7-8).
And this is His commandment: that we should believe on the name of His Son Jesus Christ and love one another, as He gave us commandment. Now he who keeps His commandments abides in Him, and He in him. And by this we know that He abides in us, by the Spirit whom He has given us. (1 John 3:23-24)Notice that it is not just in keeping the commandment to believe in Christ that we know that God abides in us, but it is also in keeping the commandment of loving one another that we have the assurance of God abiding in us.
First John 5:13 was not written in a vacuum but in a context — “these things” — and the context is about walking in light, living in righteousness and loving one another. These offer assurance that our faith in Christ is real and that eternal life — the divine life of God — really is at work in us.