Romans 1:4a

and who through the Spirit of holiness was declared with power to be the Son of God by his resurrection from the dead: Jesus Christ our Lord.

(v4, NIV)

and 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,

(v4, ESV)

Jesus was declared with power to be the Son of God. Before, Jesus was in a weak and limited state. Jesus became a man, so he was limited in certain ways. Jesus grew hungry and he got tired. Jesus got beat up, he was spit upon and he was crucified. However, Jesus was raised to kingship and power. He is the messiah king and he reigns. Jesus is no longer this weak man who gets beat up and crucified. He is now the powerful king who reigns on high. This isn't to say that Jesus shouldn't have been crucified or that Jesus couldn't avoid being beat up. Jesus did in fact choose that and it was necessary in order to save us. Jesus did it for us; he humbled himself and took upon himself our sins. Now he is declared with power to be the Son of God.