What are some lessons from the Book of 1 John?

from the old testament

• The book of 1 John is not found in the Old Testament.

from the new testament

• First John was written to warn true believers of the deceptive teachings of those who had left the believing community (1 John 2:19, 2:26). Part of the deception appears to be a weak or deficient view of sin; John reminded them that no one is, or ever has been, perfect (1:8, 10). Another deception was misrepresenting who Jesus is in some way that John doesn't explicitly say but that seems related to denying Jesus’ true humanity (4:2–3) and His divinity (5:6).
• Some believers had begun to accept some of the false teachings, so John encourages them to “walk in the light as [the Father] is in the light” (see 1 John 1:5–7).
• John's audience may also have been accepting the false teaching about Jesus, so John reminding them that he was a personal eyewitness to Jesus (1 John 1:1–3). He noted that believers knew the gospel and didn’t need more teaching because they already had the Holy Spirit’s internal witness as to the truth of the gospel (2:20, 27).
• John presented the correct view of sin by reminding believers that when we sin, Jesus is our Advocate with the Father (1 John 2:1–2). The Father willingly cleanses us of our ongoing sin when we repent of it (1:9).
• John indicates that lack of obedience may signal that someone isn't saved. This is because by keeping Jesus’ commandments “we know that we have come to know him” (1 John 2:3; cf. 3:24). John devotes a large portion of the letter reminding the believers to not be like the world (2:15–17a) but to “do the will of the Father” (2:17b), meaning to obey Him.
• John summarizes the commands in the same way Jesus did, focusing on their obedience through the lens of loving God (1 John 5:2–3) and other believers (3:14; 4:7). He explained that God’s love is manifest to the world when we love rightly (4:12).
• Some parts of the letter are difficult because they seem to suggest that believers do not sin at all (1 John 3:6–9; 5:18). John clearly didn't mean that, though, because he opens the letter saying that all sin (1:8, 10) and that no one will be perfect until Jesus returns (3:2). Those parts are best read as John contrasting true believers with those who left and are exhibiting antichrist behavior (2:18, 22–23), those who are sinning willfully and persistently. Believers, on the other hand, are being slowly perfected to be holy like God, so while they do sin, they are those who are striving for perfection through Jesus (3:3).
• John didn't intend the letter for us to use to test salvation. He clearly refers to his readers as believers (1 John 2:12–14) who know the truth (2:21) so that they come to know that they do indeed have eternal life (5:13). Given his statements about desiring that believers begin to fellowship, the letter is best read as a call for assurance through the exhortation of obedience. The more we obey Jesus, the more we will see evidence of our salvation, grow in assurance, and fellowship with other believers.
• John brings up the core deception: misunderstanding Jesus. When Jesus is misunderstood, His purpose for coming (such as to destroy sin, 1 John 3:8) is misunderstood, and, thus, salvation is misunderstood. That is why he ends his letter with a stark warning: “Little children, keep yourselves from idols” (5:21). That is, watch out for those who present a false Jesus as that is an idol.

implications for today

A slapstick trope in comedies is someone who gets bombarded by balls from the tennis machine as he tries to practice his serve. In life, Christians can feel like that tennis player, constantly bombarded not only by false religions or ideas but even false versions of Jesus. But in that case, it's no laughing matter. Within the Christian community, even some church leaders teach a different Jesus, differences that are sometimes subtle, sometimes overt. But any difference can undermine our assurance of salvation.

Three common iterations include 1) tying legalistic obedience to salvation, 2) teaching that no obedience at all is required or 3) that salvation means physical blessings, not suffering. Each teaching is based on a wrong view of Jesus.

Jesus asked, “Why do you call me ‘Lord, Lord,’ and not do what I tell you” (Luke 6:46) and said, “Blessed rather are those who hear the word of God and keep it!” (Luke 11:28). Obedience matters—-but Jesus’ commandments are not burdensome (1 John 5:3). They are summed up in love of God and love of neighbor (Matthew 22:37–40). Jesus taught that He came to give an abundant life (John 10:10), but He meant spiritual life, noting that following Him meant dying daily (Luke 9:23) and expecting persecution (John 15:20), not riches.

John taught that assurance comes from knowing who Jesus really is as fully God and fully man and why He came, to destroy sin by His death. Those who truly believe in Him are saved by Jesus’ work and, out of gratitude, strive to live like Him. No one is perfect (1 John 1:8, 10) and there will be trials in this life (James 1:2–4), but His Spirit uses them to make us more and more like Him until we see Him (1 John 3:2–3).