Short answer: First John 5:13 gives the letter's stated purpose: John writes to people who already believe in the name of the Son of God, so that they may know they have eternal life and continue to believe. The knowledge he offers rests on God's testimony about his Son, not on shifting feelings. Everything else in the letter, its tests of love, obedience and right belief, serves that aim of settled confidence and perseverance.
Why John says he wrote: the setting of 1 John 5:13
First John is a letter, not a collection of sayings, and it comes from a pastor who addresses his readers as his children. Near the end of the letter he stops to say plainly why he is writing. The verses around 5:13 are ordinary prose, moving from God's testimony about eternal life in 5:11–12 to confidence in prayer in 5:14–15. The letter reads as pastoral reassurance and correction for people unsettled by false teaching and by their own doubts. That setting matters for reading the verse: it is a deliberate statement of purpose placed near the close of a real letter to a real community.
The sentence in 5:13 rests on what comes just before it. Verses 11 and 12 give the content of God's testimony: God gave eternal life, that life is in his Son, and whoever has the Son has the life. Only then does the author name his purpose, that those who believe in the name of the Son of God may know they have eternal life. Assurance here is anchored in God's own testimony about his Son, not in the reader's performance or mood. The immediate context ties confidence to what God has said, while the wider letter keeps calling readers to examine whether love and obedience are actually present.
One pastoral caution belongs with this verse. It is not a promise of unbroken emotional certainty. The same sentence that says "that you may know that you have eternal life" also says "and that you may continue to believe in the name of the Son of God" (1 John 5:13). Continuing to believe is part of the purpose, which means assurance and ongoing trust sit together rather than competing. Pastors should resist turning the verse into a guarantee of constant good feeling. Its comfort is sturdier: it points doubting believers back to God's testimony about his Son and to the life that is found in him alone.
Why John says he wrote: that you may know
The phrase "These things I have written to you" gathers up the whole letter, not just the sentences just before it. John has argued from the beginning about light and darkness, love and obedience, the Father and the Son, true teaching and false. Now he tells his readers what all of it was for. Verse 13 is the author's own statement of purpose, and it is worth noticing that he places it near the end, after the evidence has been laid out. He is not offering a bare slogan. He is naming the goal of everything he has already written to them.
The goal is knowledge: "that you may know that you have eternal life." This is settled knowledge, not a guess or a mood. The letter has already said where that life is located. God gave eternal life, and this life is in his Son; whoever has the Son has the life (5:11–12). So eternal life here is not first a length of time but a person. To know you have it is to know you are joined to Christ. John writes so that believers can rest on God's testimony about his Son rather than on their own shifting feelings.
Notice the second half of the verse: "and that you may continue to believe in the name of the Son of God." The purpose is not a single moment of assurance but enduring trust. That keeps verse 13 from becoming a promise of unbroken emotional certainty. John's readers still had to keep believing, and so do we. Assurance is grounded in what God has said about his Son, not in how steady our feelings are. The letter aims at a knowledge that holds up over time, and it calls us back to the same place again and again: the name of the Son of God.
Why John says he wrote: that you may know
The stated purpose of the letter sits in a single sentence: John writes so that those who believe in the name of the Son of God may know they have eternal life and may continue believing. Notice who is addressed. These are people who already believe, not outsiders being introduced to the faith. The aim is assurance and perseverance, not evangelism. The verse links the two: knowing and continuing. John does not treat confidence as a one-time arrival but as something that holds a believer steady in the same trust that first brought them in.
That purpose rests on the testimony just stated. Verses 11 and 12 give the content: God gave eternal life, that life is in his Son, and whoever has the Son has the life. Assurance, then, is anchored in God's own testimony about Christ rather than in the reader's performance or mood. This matters because the letter elsewhere supplies tests of love, obedience and right belief. Those tests are real, and they call readers to examine themselves. But they function within the argument, not as the foundation. The ground of confidence is what God has said about his Son.
Verses 14 and 15 show what this confidence produces: boldness in prayer, asking according to God's will, with the assurance that he listens. The letter moves from settled identity to lived dependence. A pastor should be careful here. Verse 13 is not a promise of unbroken emotional certainty. The same verse speaks of continuing to believe, which assumes seasons where belief must be held rather than felt. Assurance is grounded in God's testimony, and the call to keep believing is how that assurance is lived out day by day.
What 1 John 5:13 says about why the letter was written
The verse states the purpose plainly: John writes so that those who believe in the name of the Son of God may know they have eternal life. Notice the order. The readers already believe; the letter aims at their confidence, not at their conversion. Notice also where the knowledge rests. In the verses just before, life is located in the Son, and having the Son is what gives the life (5:11–12). John does not tell his readers to generate assurance by examining their feelings. He points them back to God's testimony about his Son and to the faith that receives him.
Careful readers differ here. Some treat the letter's tests of love and obedience as evidences a believer examines, so assurance rises and falls with visible fruit. Others read those tests as descriptions of what genuine faith always produces, with assurance resting chiefly on God's testimony about his Son and the tests confirming it. Readers also differ over whether "you may know" promises settled, conscious assurance to every believer or names the goal the letter pursues, a goal believers may still struggle to feel. Some tie the letter tightly to false teachers who denied Jesus came in the flesh; others stress its general pastoral setting.
The text sets its own limits. It addresses people who already believe, grounds life in having the Son, and closes by naming continued believing as the aim, not a one-time feeling. So pastors should not turn this verse into a guarantee of unbroken emotional certainty. Across these readings one thing stays central: eternal life is God's gift in his Son, received by faith, and the letter was written to strengthen confidence in him rather than in our own moods or performance.
Across these readings one thing stays central: eternal life is God's gift in his Son, received by faith, and the letter was written to strengthen confidence in him rather than in our own moods or performance.
Why John says he wrote: that you may know
First John 5:13 states the letter's purpose plainly: John writes to people who already believe in the name of the Son of God, and he writes so that they may know they have eternal life. Notice the order. Belief is assumed, not produced, by the sentence. The readers are not outsiders being introduced to Jesus but insiders being steadied. The previous verses supply the content of what they are to know: God gave eternal life, and that life is in his Son. Assurance, then, is not a new revelation but a clear sight of what God has already testified concerning Christ.
The verse ties knowing to a person, not to a feeling or an argument. Eternal life is not a reward for spiritual insight; it is life located in the Son and given by God. So John's purpose is christological at its root. The more clearly Christ is seen as the one God sent, the more solid the confidence of the believer becomes. The gospel is assumed throughout: God gave his Son, and in giving the Son he gave life. John writes so that readers might rest on that gift rather than on the shifting quality of their own awareness.
Pastors should be careful here. Verse 13 is not a promise of unbroken emotional certainty. The same verse names continuing to believe as its aim, and the letter grounds assurance in God's testimony about his Son, not in how a person feels on a given day. Some sincere believers will read this and find their feelings quiet while their trust in Christ remains real. The verse meets them there. Assurance grows as Christ is seen and trusted, and the letter's purpose is to keep pointing readers back to him.
Why John wrote: that you may know
Verse 13 states the letter's purpose plainly: John writes to people who already believe in the name of the Son of God, so that they may know they have eternal life and may continue to believe. Notice the two halves. Assurance is the goal, and perseverance is the goal, and John does not set them against each other. The verse rests that assurance on something outside the reader. Just before it, the testimony is that God gave eternal life, and that this life is in his Son; the one who has the Son has the life. So when doubt presses, the pastoral move is not to inspect your feelings but to return to those plain statements about the Son.
Read the whole letter with verse 13 in view. John has given tests of love and obedience, and those tests are meant to confirm God's testimony about his Son, not to replace it. If you make your own performance the foundation, assurance will rise and fall with your week. If you make Christ the foundation, the tests become evidence of life rather than the ground of it. This is why the letter can call readers to continue believing and still say the purpose is that they may know. Grace comes first: God gave the life, and it is in his Son. Your response rests on that gift, not on maintaining a steady emotional state.
Assurance is not a promise of ease. The verses that follow tie prayer to God's will: we ask with boldness because he listens, and we ask according to his will, not as a claim on every outcome we want. So let assurance produce honest, specific prayer rather than certainty about results. Pursue continued believing through ordinary means: hearing the letter read and taught, praying, gathering with others who confess the same name. Verse 13 names continued believing as something to pursue, and it grounds that pursuit in grace. Pastors should be careful here. This verse does not promise unbroken emotional certainty; it promises that the testimony about the Son is true, and that those who have him have life.
This verse does not promise unbroken emotional certainty; it promises that the testimony about the Son is true, and that those who have him have life.
Biblical fidelity check
Verse 13 reads as the letter's own statement of purpose: "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." The phrase "these things I have written" gathers up everything before it, so the purpose is not a single paragraph but the whole letter. "That you may know" is the language of settled knowledge, and "eternal life" is defined by the verses just before it as life that is in the Son. The risk here is treating assurance as a feeling to be chased, or as a verdict that rises and falls with yesterday's obedience.
Evangelical readers differ over how the letter's tests function. Some read them as evidences a believer examines, so assurance tracks visible love and obedience; others read them as describing what genuine faith always produces, with assurance resting chiefly on God's testimony about his Son. Readers also differ over whether "you may know" promises stable, conscious assurance to every believer or names the intended goal some still struggle to feel. What stays central is that eternal life is God's gift in his Son, received by faith, and that the letter was written to strengthen confidence in him.
Related studies for 1 John 5:13
For further study, compare the stated purpose here with the openings of the letter 1 John 2: Light, Love, and Abiding, the role of God's testimony about his Son 1 John 5: Faith Overcomes the World, the place of love and obedience as evidence 1 John 1:5–10: Walking in the Light, and the call to persevere in faith 1 John Bible Study Guide: Summary, Themes, Outline.
Frequently asked questions
Why did John write 1 John, and who was he writing to?
John wrote to people who already believed in the name of the Son of God, not to outsiders who had never heard the gospel. In 1 John 5:13 he states the aim directly: that they may know they have eternal life and continue to believe. The letter is therefore a pastoral letter to a believing community, written to steady them rather than to recruit them. Its teaching on love, obedience and truth serves that purpose of assurance and perseverance.
Does 1 John 5:13 promise that every believer can be certain of salvation?
The verse promises knowledge, but it grounds that knowledge in God's testimony about his Son rather than in the intensity of a person's feelings. John writes that believers may know they have eternal life, and the surrounding verses locate that life in the Son. This is real assurance, yet the same verse speaks of continuing to believe, so certainty is not a claim to unbroken emotional confidence. Pastors should be careful not to turn the verse into a guarantee of constant good feeling. The confidence offered is settled trust in what God has said, held while faith continues.
How do the tests in 1 John relate to the assurance this verse describes?
The tests of love, obedience and right belief are not a second gospel added to grace; they serve the stated purpose of 1 John 5:13. John gives them so that readers can examine whether the life he describes is actually at work in them, and so that genuine faith may be confirmed rather than doubted. They function as evidence, not as the ground of acceptance, which remains God's gift of life in his Son. Read this way, the tests strengthen assurance and call readers to keep believing.
