Verse 14 – We the believers, because we have the Spirit, know that God sent His Son to save the world. We have seen that it is true. Also, because we have the Spirit, we testify of the gospel. It all hinges on salvation. Since we have salvation we see and testify of the gospel.
Verse 12 – “No one has ever seen God at any time; if we love one another, God abides in us and His love is perfected in us.”
No one has seen God, but if we love the brethren God dwells in us. We cannot see him, yet He is in us. But He is seen in us. Does that make sense? No one has seen God, but He shows Himself through believers when we love each other. When that happens, it means that He abides in us and that He is perfecting His life in us. So, love one another. It is a vital part of the Christian's life.
Verse 13 – The Spirit is the evidence of our salvation. It is the evidence of God’s abiding in us. Ah, but how do we know that the Spirit is in us? That’s an easy one. The fruit of the Spirit show us that the Spirit is in us. Galatians 5 clearly shows us what the Holy Spirit produces in believers, so look at the fruit. They are evidence of the Spirit. The Spirit is the evidence of God abiding.
