1 John 4:13
13 Hereby know we that we dwell in him, and he in us, because he hath given us of his Spirit.
John here gives us a proof that we dwell in Jesus and He in us. We know that because we know that He gave us the indwelling Holy Spirit. We receive the Spirit when we believe in Jesus. That’s when we become a new creation and receive a new heart. The Holy Spirit takes up residence in us. We are the temple of the Holy Spirit. (1 Corinthians 6:19)
John proclaims that having the Holy Spirit is important. He leads us into all truth. “6 We are of God: he that knoweth God heareth us; he that is not of God heareth not us. Hereby know we the spirit of truth, and the spirit of error” (1 John 4:6). John also said this in the Gospel of John. “13 Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come” (John 16:13).
It’s through the Spirit we say that Jesus came in the flesh. “2 Hereby know ye the Spirit of God: Every spirit that confesseth that Jesus Christ is come in the flesh is of God:3 And every spirit that confesseth not that Jesus Christ is come in the flesh is not of God: and this is that spirit of antichrist, whereof ye have heard that it should come; and even now already is it in the world” (1 John 4:2-3).
The spirit of antichrist is in the world today. Plenty of people talk about God. Doesn’t seem like anyone is anti-God, but plenty of people are anti-Christ. It’s the Spirit within that says Jesus came in the flesh, died on the cross for our sins, and rose again. It’s the Spirit who says we have been saved by grace through faith. God sent His Son into the world. He wasn’t a phantom, a ghost, or a spirit. He came as a man and fulfilled the law as a man and died on the Cross as a man—the Son of Man.