Every careful Christian has considered the vexing question of assurance. What is the ground of my salvation? What is the ground of my confidence in salvation? How can I know that I am right before God?
As we work through the second cycle of tests, John interrupts his argument to address the important subject of assurance. In using the phrase “and by this” John is referring to what has just gone before. Loving in deed, and not just in word, enables us to assure our hearts (v. 19). Then it is important to notice how John moves in a direction than we might expect. He brings in God’s omniscience as a basis for confidence in those times when your heart condemns you (v. 20). Notice that God’s omniscience is not made the basis for condemnation — just the reverse. And when our hearts are confident, we don’t have the problem (v. 21).
Obedience to the command of God is related to answered prayer. Those who reject God’s basic instruction have no basis for approaching Him with petitions. Those who listen to Him have that assurance (v. 22). And lest we imagine what obedience means, John is careful to spell out what he is talking about. This is the commandment; we are to believe and love (v. 23). Believe what? In the Lord Jesus Christ. Love whom? One another. Then we are called to abide in that obedience. The one who is obedient to this command abides, or remains, in Him. Conversely, Christ abides in him. We know this by the Spirit given to us. The presence of this Spirit is not identified by warm tinglies, but rather, the indwelling Spirit guides and leads us into an objective belief in Jesus, and an objective love for the saints (cf. Rom. 8:13-14)
John then returns to his theme, and addresses the doctrinal aspect of genuine Christianity. First is believing skepticism. Genuine Christian faith can be measured by its unbelief. “Beloved, do not believe . . .” In a world in which evil exists, such lack of belief is absolutely necessary. The antithesis is between right and wrong, not spiritual and physical (4:1). False prophets exist, and we shouldn’t ever believe them. Then there is knowledge of the Spirit. John is writing at a time when believers had to sort out whether prophecies were false or true. But just the fact of “inspiration” did not make something right. Even the spirits must be required to subscribe to the creed. The content of this creed concerned the incarnation. This is what was required: Jesus of Nazareth is the Christ enfleshed (v. 2). Notice that the spirit which does not confess this is not of God. This is different from a spirit which positively denies the truth. For John, the absence of such a confession was sufficient to reject such a spirit. Then we come to Antichrist. The spirit of Antichrist is doctrinal error within the Church, and not political tyranny (v. 3).
So we have been discussing how a teacher is tested doctrinally. John then turns to discuss how auditors are tested. The one who gives his ear is as responsible to hear the truth as the messenger is to speak it. True listeners are greater than false speakers because the Lord is in them, and He is greater than all (v. 4). Then there are worldly listeners. The false speakers are worldly and consequently they find a ready and willing audience in the world. The world hears them (v. 5). True apostolic authority also exists. The apostles are from God. This means that someone who knows God will also know and recognize His messengers. Conversely, one who does not know God will treat His emissaries with contempt. Here then is the basic distinction—apostolic Christianity is marked by this . . . listening to the apostles.