Lesson 22: Three Great "We Know" Affirmations

1 John 5:18-21 · The Believer's Certainty and the Final Warning

The letter began with an eyewitness testimony to the Word of Life. Now it ends with three great affirmations — three "we know" declarations that sum up everything John has written. The believer's assurance is not a fragile hope but a settled certainty grounded in Christ. But John does not end with abstract theology. He ends with a personal, urgent command: "Little children, keep yourselves from idols." The letter closes where it began — with fellowship with the true God, and a warning against everything that would steal our hearts away from Him.

Read the Text

¹⁸We know that everyone who has been born of God does not keep on sinning, but he who was born of God protects him, and the evil one does not touch him. ¹⁹We know that we are from God, and the whole world lies in the power of the evil one. ²⁰And we know that the Son of God has come and has given us understanding, so that we may know him who is true; and we are in him who is true, in his Son Jesus Christ. He is the true God and eternal life. ²¹Little children, keep yourselves from idols.
— 1 John 5:18-21 (ESV)

We Know — The Threefold Certainty

John uses the word "know" three times in these four verses. This is not the knowledge of academic study but the settled confidence of personal experience — the certainty that comes from being in relationship with the One who is truth. Each "we know" addresses a distinct area of assurance:

Verse 18: We know our security — the one born of God is kept by Christ and the evil one cannot touch him.
Verse 19: We know our identity — we belong to God, not to the world system that lies in the devil's power.
Verse 20: We know our knowledge — the Son of God has given us understanding to know the true God and to be in His Son.

Together, these three affirmations form the capstone of everything John has written. The moral test, the love test, the doctrinal test, and the Spirit's witness all converge on this single point: we know that we belong to God.

First Affirmation: Security in Christ

Verse 18: "We know that everyone who has been born of God does not keep on sinning, but he who was born of God protects him, and the evil one does not touch him."

The first affirmation addresses our security. The phrase "does not keep on sinning" echoes 3:9 — the one born of God cannot live in habitual, unrepentant sin because God's seed abides in him. The new nature does not practice sin as a way of life.

But the emphasis here is not on our responsibility but on Christ's protection. "He who was born of God" refers to Jesus — the only-begotten Son. Jesus Himself is the protector of everyone who has been born of God. He keeps us safe, and the evil one — Satan — cannot "touch" us. The word "touch" (haptomai) means to grip, to lay hold of with harmful intent. Satan can tempt, accuse, and harass, but he cannot lay hold of the one who is held by Christ. Our security is not in our grip on Him but in His grip on us.

Two "Born of God" ReferencesVerse 18 uses the phrase "born of God" in two distinct ways. The first refers to believers — "everyone who has been born of God." The second refers to Christ — "he who was born of God." The same Greek construction (ho gennētheis ek tou theou) is used of Christ, emphasizing His unique, eternal sonship. He is the protector; we are the protected. This is the gospel in a single verse: the Son keeps the children safe from the evil one.

Second Affirmation: Identity in God

Verse 19: "We know that we are from God, and the whole world lies in the power of the evil one."

The second affirmation addresses our identity. There are only two families in John's view: those who are "from God" and those who belong to the world system that "lies in the power of the evil one." The contrast could not be sharper.

The phrase "lies in the power of the evil one" paints a vivid picture. The Greek word keimai means to lie down, to recline, to be held in place. The world is not merely influenced by the devil — it is cradled in his arms, held in his bosom, lying passive in his power. This is the world system John has warned about throughout the letter — the lust of the flesh, the lust of the eyes, and the pride of life.

But the believer's identity is different: "we are from God." This is not our achievement but our origin. We have been born of God, transferred from the domain of darkness into the kingdom of His beloved Son (Colossians 1:13). We are no longer citizens of the world system. Our citizenship is in heaven.

Third Affirmation: Knowledge of the True God

Verse 20: "And we know that the Son of God has come and has given us understanding, so that we may know him who is true; and we are in him who is true, in his Son Jesus Christ. He is the true God and eternal life."

The third affirmation addresses our knowledge. The Son of God has come — the incarnation is a historical reality, not a myth. And He has given us understanding (dianoia) — not natural intelligence but spiritual comprehension, the ability to perceive spiritual reality. This understanding enables us to know Him who is true — the Father, the true God.

John's language echoes the Gospel of John 17:3: "And this is eternal life, that they know you, the only true God, and Jesus Christ whom you have sent." Eternal life is knowing God. And that knowledge is not a human achievement — it is a gift from the Son who came to reveal the Father.

The verse ends with the highest Christological declaration in the letter: "He is the true God and eternal life." The "He" refers to Jesus Christ. John could not state the deity of Christ more plainly. The Son of God is Himself the true God. He is not merely a way to eternal life — He is eternal life. To know Him is to know God. To have Him is to have life.

ReflectionThree "we know" affirmations. Security: the evil one cannot touch us because Christ holds us. Identity: we are from God, not from the world that lies in the devil's power. Knowledge: the Son has given us understanding so that we know the true God and are in Him. This is not the arrogant certainty of a know-it-all but the quiet confidence of a child who knows his Father. John wrote that we might know — and here, at the end, he declares that we do.

The Final Command: Keep Yourselves from Idols

Verse 21: "Little children, keep yourselves from idols."

After all the theology — the three tests, the great declarations, the witnesses, the "we know" affirmations — John ends with a simple, personal command. It is the last word, the final exhortation, the practical application of everything he has written.

The word "idols" (eidōla) refers to anything that takes the place of God in the heart. In John's day, that often meant literal idols — statues of pagan gods. But John's use is broader. An idol is anything that competes with God for your affection, your trust, your worship. It can be money, status, relationships, comfort, reputation — anything you look to for what only God can give.

The verb "keep" (phylassō) means to guard, to watch over, to protect. It implies vigilance. Idols do not announce themselves. They creep in subtly, taking the place of God in small increments. The heart is an idol factory, and the only safeguard is constant watchfulness.

John ends where he began — with fellowship. The letter opened with the call to fellowship with the Father and the Son (1:3). It closes with the warning against anything that would disrupt that fellowship. The true God is life. Everything else is a cheap substitute. Keep yourselves from idols.

The Letter Complete

John's first epistle is a masterpiece of pastoral wisdom. He has given us four purposes — joy, holiness, discernment, and assurance. He has given us three tests — the moral test, the love test, and the doctrinal test. He has given us three witnesses — the Spirit, the water, and the blood. He has given us great declarations — God is light, God is love. And he has given us one command that sums up everything: believe in the Son of God and love one another.

The letter ends where all true theology ends — not in abstract knowledge but in worship and watchfulness. We know the true God because He has made Himself known in His Son. And because we know Him, we guard our hearts against everything that would steal our love from Him. The knowledge of God is eternal life. Keep yourselves from idols.

Key Terms to Remember

Does not keep on sinning — The one born of God does not live in habitual, unrepentant sin. Not sinless perfection but a life whose settled direction is obedience, not rebellion.
He who was born of God protects him — Jesus Christ, the unique Son of God, is the protector of every believer. Our security is not in our grip on Him but in His grip on us.
The evil one (ho ponēros) — Satan, the devil. He can tempt, accuse, and harass the believer, but he cannot "touch" (lay hold of) the one who is held by Christ.
Lies in the power of the evil one — The world system is not merely influenced by Satan but is cradled in his arms, lying passive under his power. The believer, by contrast, is "from God."
Understanding (dianoia) — Spiritual comprehension, the capacity to perceive spiritual reality. A gift from the Son that enables us to know the true God.
He is the true God and eternal life — The highest affirmation of Christ's deity in the letter. Jesus Christ is not merely a way to God — He is Himself God, and He is eternal life personified.
Idols (eidōla) — Anything that takes the place of God in the heart. The final warning of the letter: guard your hearts against every competing affection.

Check Your Understanding

1. What does John mean when he says "the evil one does not touch him" (v. 18)?

a) That believers will never experience temptation or difficulty

b) That Satan cannot lay hold of the one who is protected by Christ

c) That the devil has no power at all in the world

d) That believers are immune to all harm

b) That Satan cannot lay hold of the one who is protected by Christ. The word "touch" means to grip, to lay hold of with harmful intent. Satan can tempt, accuse, and harass — but he cannot finally lay hold of the one who is held by Christ. Our security is not in our strength but in our Savior. "He who was born of God" — Jesus Himself — protects us. This is the believer's security: the Good Shepherd holds His sheep, and no one can snatch them out of His hand (John 10:28-29).

2. What contrast does John draw in verse 19 between believers and the world?

Believers are "from God" while the whole world "lies in the power of the evil one." There are only two families, two origins, two allegiances. The world system is not neutral — it lies passive in the devil's arms, cradled in his power. But the believer has been born of God, transferred from the domain of darkness into the kingdom of Christ. Our identity is not defined by the world we live in but by the God we belong to. We are in the world but not of it.

3. What does John affirm about Jesus Christ in verse 20?

That He is "the true God and eternal life." This is the highest Christological statement in the entire letter. Jesus is not merely a prophet, a teacher, or a way to God — He is Himself God, and He Himself is eternal life. To know Him is to know God. To have Him is to have life. John began the letter by declaring that the Word of Life was with the Father from the beginning. He ends by declaring that this same Jesus is the true God — the full deity of Christ is the foundation of everything John has written.

4. Why does John end the letter with the command "keep yourselves from idols" (v. 21)?

Because the knowledge of the true God demands that we guard our hearts against every competing affection. After giving us the highest theology — "He is the true God and eternal life" — John immediately warns us against anything that would displace Him. An idol is anything that takes the place of God in the heart. The verb "keep" implies constant vigilance. The letter began with fellowship (1:3) and ends with a warning against anything that would disrupt it. True knowledge of God always leads to practical holiness — we guard what we treasure.

Primary Resource

Read: Adrian Rogers, "A Know-So Salvation" and "Dealing with Doubt" — sermons covering 1 John 5:18-21. Rogers emphasizes that the three "we know" affirmations provide absolute assurance of salvation, and that the final command to keep from idols is the practical application of all Christian truth.

Read: 1 John 5:18-21 in at least two translations (e.g., ESV and NIV or KJV). Pay close attention to how "keep yourselves from idols" is translated, and notice how different translations render the final affirmation of Christ's deity.

Review: The Letter Complete

Congratulations — you have now completed the verse-by-verse study of 1 John. You have traced the flow of thought through all five chapters, learned the three tests of genuine faith, and encountered key Greek terms. The mission was to deepen your walk with God through this letter — may the fellowship John promised be your daily reality. If anything throughout these lessons remains unclear, ask me — I'm your teacher and can help with any question.

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