The Trinity is a mystery of the Christian faith. How can God be only one God but also three Persons? How can 1 equal 3 and 1 + 1 + 1 = 1? The Athanasian Creed tries to explain it; no one can fully understand it, but we must rather receive it by faith. (What does God's Word say?) John 3:16 presents another divine mystery. Let's take a look.
This mystery had to be revealed to us; we couldn't have found it otherwise. The verse describes how the Trinity works. "God [the Father] so loved the world." - Where is God when bad things happen, when people die? God's love then is hard to see. But it's still there. When man sins, God's love remains, for He has promised us "everlasting love" according to Isaiah - agape. God loves the repulsive. God loves the world!
"He gave His only-begotten Son." Note that God didn't send His Son; that's not what love is. Instead, He gave Him. This love is too profound for our sinful selves, so we try to downplay it. But the reality remains: as the Father gave us the Son, so the Son also gave Himself for us, bearing our deserved punishment to give us salvation.
So also God the Holy Spirit comes to give us faith to believe in God the Son. If we don't believe in something, it won't benefit us - a buried treasure that you don't think is there, so you won't dig for it. Therefore we need the Holy Spirit to enable us to believe in Jesus our Substitute. As the Word is proclaimed to us, the Holy Spirit uses it to speak to us, to convince us that the Christ-proclaiming Scriptures are true. Everyone who has this faith will be saved. Amazingly, it doesn't matter what sins you commit (although you are to stop sinning!). They're all washed away in the God-given Son's blood. Therefore Christianity is not a deal between you and God - God does ALL the giving. We simply receive.
This excellent sermon came to us today from one of the Preus lineage. Those who were there know which one.