Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son. – 1 John 5:10 ESV
John has mentioned three witnesses that testify to the truth of Jesus' claim to be the Messiah, the Son of God. “For there are three that testify: the Spirit and the water and the blood; and these three agree” (1 John 5:7-8 ESV). Then he adds the testimony of God Himself. “If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son” (1 John 5:9 ESV). Even God the Father has testified on the behalf of Jesus, declaring Him as His Son and claiming to have sent Him to “to bring good news” and “to proclaim that captives will be released and prisoners will be freed” (Isaiah 61:1 NLT). But John had more evidence to add to his argument. So far, his proof has all be external in nature – the baptism of Jesus, His crucifixion, the coming of the Spirit, and the verbal acknowledgement of God. Now he brings us the testimony within – the very indwelling presence of the Spirit of God that every believer receives upon acceptance of Jesus as their Savior. The apostle Paul tells us, “but you have received the Spirit of adoption as sons, by whom we cry, ‘Abba! Father!’ The Spirit himself bears witness with our spirit that we are children of God” (Romans 8:15-16 ESV). When brought before the Jewish council, Peter said, “The God of our fathers raised Jesus, whom you killed by hanging him on a tree. God exalted him at his right hand as Leader and Savior, to give repentance to Israel and forgiveness of sins. And we are witnesses to these things, and so is the Holy Spirit, whom God has given to those who obey him” (Acts 5:30-32 ESV).
The Holy Spirit is living proof of Jesus' messiahship. The very presence of the Spirit within the life of the believer should unequivocally convince us of any of His other claims. Jesus told His disciples that the Holy Spirit would come. “And I will ask the Father, and he will give you another Helper, to be with you forever, even the Spirit of truth, whom the world cannot receive, because it neither sees him nor knows him. You know him, for he dwells with you and will be in you” (John 14:16-17 ESV). He had told them that the Holy Spirit would testify to them regarding Him. “But when the Helper comes, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will bear witness about me” (John 15:26 ESV). And that's exactly what the Spirit does. He bears witness, testifies and gives evidence of Christ's life-changing, heart-transforming power in the life of the believer. “So all of us who have had that veil removed can see and reflect the glory of the Lord. And the Lord—who is the Spirit—makes us more and more like him as we are changed into his glorious image” (2 Corinthians 3:18 NLT).
We have the very Spirit of God within us, empowering, equipping and testifying. His presence should make a profound difference in the way we live our lives. Paul explains it quite succinctly. “But the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control; against such things there is no law. And those who belong to Christ Jesus have crucified the flesh with its passions and desires” (Galatians 5:22-24 ESV). As we see that fruit produced in our lives, we can know that Jesus' death and resurrection are what made it possible. Had Jesus not died, rose again, and ascended back into heaven, the Holy Spirit would not have come. His presence here is proof that Jesus sits at the right hand of the Father, and that someday He is going to return to this earth to finish what He began. He will restore this world back to its original God-ordained glory. He will destroy sin and death once and for all. He will remove all pain, sorrow, tears, heartache and any other evidence of the fall – forever.
The evidence is overwhelming in favor of Jesus. He is the Son of God. He is the Savior of the world. He is the long-awaited Messiah whom the prophets of old had long-ago predicted. And over the last 2,000 plus years, His claims have been proven true by the miraculous spread of the Good News of Jesus Christ around the world. Millions have come to faith in Christ, of all walks of life and every conceivable people group. And the Kingdom continues to expand. The Holy Spirit is hard at work, guiding, motivating, sending, and equipping God's people to do His Work. But at the end of the day it all boils down to a fairly simply formula: “Whoever has the Son has life; whoever does not have the Son of God does not have life” (1 John 5:12 ESV).