Christians believe that Jesus is the Son of God. But what does that mean? Does that mean that Jesus has always been the Son of God or that God really liked Jesus and adopted him as the Son of God?
One of the key verses in this discussion is:
“[Jesus] was declared to be the Son of God in power according to the Spirit of holiness by his resurrection from the dead, Jesus Christ our Lord.” (Romans 1:4 ESV)
That kind of looks like Jesus became the Son of God at his resurrection. That would be a problem for traditional Christian theology.
I would suggest that “declared” means more that he was revealed as the Son of God. That is, questions about his relationship to the Father were resolved by his resurrection. The Father would not have raised Jesus if Jesus had been lying about their relationship. The resurrection validates all that Jesus had claimed.
Having said that, it could be argued that this is just wishful thinking on my part. It would help if this could be demonstrated to already be a part of Paul’s way of thinking. Well, I’m glad that you asked.
Paul argues that Christians are already children of God.
“The Spirit himself bears witness with our spirit that we are children of God.” (Romans 8:16 ESV)
In the same chapter, Paul also argues:
“And not only the creation, but we ourselves, who have the firstfruits of the Spirit, groan inwardly as we wait eagerly for adoption as sons, the redemption of our bodies.” (Romans 8:23 ESV)
As with Jesus, there is a connection between our relationship with the Father and our resurrection. Like Jesus, our relationship does not begin at the resurrection but is fully revealed at our resurrection. People can say what they want about Christians now, but at the resurrection there can be no disputing that we are sons and daughters of God.
So was Jesus adopted as the Son of God? Not at all. Jesus has been the Son of God for all eternity. But that Sonship was revealed in a new way at his resurrection.