“Don’t reflexively believe everything you hear.” This is the gist of the commandment at 1 John 4:1, and the inspired penman goes on in the same statement to explain why Christians should “vet” or verify as true every doctrine or claim made by someone who professes to speak on behalf of God – because many “pseudo” prophets are present in our world. Conscientious Christians try to see the good side of people and give others the “benefit of the doubt,” but these good traits DO (potentially) leave us open to being misled by people with unscrupulous motives. In vv. 2-6, John’s words emphasize the same point Peter had made in Acts 4:12, that there is NO “alternative” to Jesus when it comes to salvation from sin. In the immediate context of John’s time these words would stand as a rebuke to the “Gnostic” false teachers who were beginning to trouble the church at the end of the first century. Among other things, they taught that Jesus was merely a man who died on the cross, while Christ was an entirely separate entity, the spirit of God (who merely “inhabited” Jesus up to the crucifixion). In a twenty-first century context, John’s words here form a rebuke of the religious pluralism and egalitarianism that are so much fixtures of modern christendom’s perspective. (Religious pluralism asserts that the denominational divisions of christendom constitute the “branches” on the “vine” in John 15:1-8. Religious egalitarianism says that all religious beliefs – including those which do not include belief in Jesus – are all equally valid and effective for salvation from sin.)
From 1 John 4:7 through 5:3, John explains how God is Himself the “definition” of real love. The practical application he makes in 4:7-8 is that for Christians to genuinely love others, our motives and actions should mirror God’s. In His incarnation (Hebrews 2:9 & 17) and sacrifice, Jesus provides the ultimate illustration of what it means to love as God does – He put the (eternal) comfort and welfare of others ahead of His own (cf. 1 John 4:9-11).
Christians are able to love one another (and others) in the same way God does because His example of love – in providing Jesus to redeem us – demonstrates what “love” actually means. Just as Jesus by His actions embodies and reflects for all people what the love of God really is, John points out in vv. 20-21 that claims of love will be exposed as lies by hateful actions that contradict the Father’s commandment that we should LOVE each other. God commands love among His children (5:1-3) and this should not be a “burdensome obligation” to fulfill. As our Maker, it is not unreasonable on His part for God to require that His children love one another, because there is no one He is unwilling to love and save (even though many people freely reject His love, and therefore the salvation He offers them).