Unity with God is distinct from equality with God. Jesus did not make himself equal to God, even though the accquation of same is what got him crucified. Resurrection is his vindication. Jesus subordinates himself to God as son, not to be confused with the heretical subordination, as in God existing before Jesus. The resurrection of JC confirms that God's Kingly rule is present in him.
Confirmation also has a retroactive thrust.
Harkens back to John's baptism, thence to his conception and birth. Doesn't stop here, but proleptic revelation in unfinished earthly history manifests the eternal Son. So we go beyond earthly existence, back to time before, reflects eternal identity of Father. Crucified JC exalted to fellowship with Father and participation in Lordship. Cites Athanasius, who says the Father can not be the Father without the Son and so is never without the Son.