Romans / Question
Romans 1:3-4 presents Jesus as both the promised son of David and the Son declared in power by resurrection from the dead. Paul holds together Jesus' place in Israel's story and his resurrection authority as Lord.
Paul opens Romans by saying the gospel concerns God's Son. That Son comes from David's line according to the flesh and is marked out in resurrection power according to the Spirit of holiness.
This keeps the gospel rooted in the story of Scripture. Jesus is not an abstract religious figure; he is the promised king whose resurrection announces his lordship.
A careful reading keeps together the verse into two different Jesuses. Paul is describing one Son through two lenses: promised lineage and resurrection power.