Today, we see a view of the likeness between the Father and Jesus His Son based on a concept akin to biological genetic inheritance. There is an idea of a sharing of the substance of what the Father is. Trinitarians call this "homoousios."
What is our understanding of being born again? It can typically be seen as redoing what did not work the first time. The first birth we undergo is a natural biological inheritance of a physical body. While it results in good biological substance of the human being, it often leads to a mess. We might end up as criminals, murderers, liars, or deviant in various ways—attributes not suitable for eternal harmonious fellowship with the Father. Thus, we need to do it again, differently. It requires a rebuild of our lives, but not like our first birth, which fails to achieve righteous saintliness. Instead, we need to build our lives again based on the Son of God, the light of the world, the Christ, Jesus, sent by the Father for this purpose.
We need to believe in this light of the world and strive to understand and obey His teachings. We do so with the assurance that, as Jesus taught, we will know the truth, and the truth will set us free. This is called being born again, and it holds the prospect, since the Father raised Jesus from the dead, of leading us toward eternal harmonious fellowship with the Father, as we live by the teachings given to Jesus for us by the Father. It is spiritual because it is based not on biological inheritance, but on teachings from heaven that came through Jesus, the light of the world, sent by the Father.
Now back to the first topic: the likeness between the Father and Jesus His Son. It is not like biological inheritance. It is not about sharing a biological substance of what the Father is. It is not some substance passed to Jesus from the Father during conception. It is a likeness based on the same principle we find in being born again. The Father loves the Son as His only begotten Son and teaches Him everything He can teach, giving Him everything He can give. The Father knew that He would have a person subject to Him as the ultimate king, with whom He would have better options than the hire-and-fire options He has with earthly kings.
Kings like biblical Saul could be anointed, appointed, and commanded, but ultimately could be kept or fired if things went well or badly. God has power over them, but it is coarse-grained. A Son, on the other hand, is one whom God could not only command but also teach and correct, to avoid the nuclear option. The Christ, Jesus, is the main one foretold to David to be this Son who would build the temple rightly. Solomon was the initial fulfillment, but it established hope of even greater fulfillment in a true Christ, the only-begotten Son.
The Father is therefore manifestly seen in this Son because the relationship allows Him to show His own ways through this Son by correcting, teaching, and helping Him in all of the ways of God, His heavenly Father. This likeness of the Father seen in Jesus His Son is not some philosophically presumed substance like a kind of DNA of God. It is the same kind of likeness we can have when we are born again. It is a likeness that comes from a life built on the Father’s teachings given to His Son.
