Son of God?
While the use of "son" was metaphorical in 5:19, the use of "son" as in the "son' or the "son of God" in most sectarian Bible versions is a slight mistranslation.* The word "son" has been translated from the Greek word υἱός (huios). While this could indicate a relationship of offspring (father/son), this is only in a "in a restricted sense, the male offspring (one born by a father and of a mother)"
But it is important not to confuse Jesus' metaphors with himself. In the same way that we would not confuse God with a master of slaves in another of Jesus' analogies.
This is why Jesus uses the Greek word γάρ (gar) - which refers to the previous statement in similarity. Thus this can also be translated to "similarly" as well. According to Thayer's lexicon, the "succeeding statement contains the reason for its immediate predecessor," and "it serves to explain, make clear, illustrate, a preceding thought or word." In this case, Jesus' statement here explains the metaphor about the son and the father in John 5:19.
When relating to Jesus' relationship with God, the more accurate translation* of the word υἱός (huios) as taken from the Greek lexicon, is "one who depends on another or is his follower."
Thus the word more closely means "devoted one" or "loving servant."
In the sense of a teacher such as Jesus, it could also be accurately construed to mean "representative" as in God's representative.
Did God have only one son?
The concept that sectarians have claimed, of God begetting only one son makes no sense and does not agree with scripture.
Besides, why would God only beget one son? Would the Supreme Being, the Controller of all creation, somehow be limited in His ability to beget children? Most men can theoretically beget tens if not hundreds of children in their lifetime. And we are saying that the Supreme Being can only beget one person? Is God now impotent? This is simply illogical.
This also contradicts other verses elsewhere in scripture. We find many verses utilize refer to multiple devoted children of God:
When men began to increase in number on the earth and daughters were born to them, the sons [בֵּן (ben)] of God saw that the daughters of men were beautiful, and they married any of them they chose. (Genesis 6:1-2)
The Nephilim were on the earth in those days — and also afterward — when the sons [בֵּן (ben)] of God went to the daughters of men and had children by them. (Genesis 6:4)
[Jesus speaking] “Blessed are the peacemakers, for they will be called sons [υἱός (huios)] of God.” (Matthew 5:9)
...Adam, the son [υἱός (huios)] of God. (Luke 3:38)
[John, speaking of Jesus] Yet to all who received him, to those who believed in his name, he gave the right to become children [υἱός (huios)] of God. [John 1:12].
"Therefore, brothers, we have an obligation—but it is not to the sinful nature, to live according to it. For if you live according to the sinful nature, you will die; but if by the Spirit you put to death the misdeeds of the body, you will live, because those who are led by the Spirit of God are sons [υἱός (huios)] of God." (Romans 8:12-17)
“You are all sons [υἱός (huios)] of God through faith in Christ Jesus.” (Galatians 3:26)Here we can see a consensus of the use of “sons of God” within scripture. Yes, these translations utilize "son" - but their source comes from υἱός (huios) in Greek and בֵּן (ben) in Hebrew - both referring to "devoted followers" or "loving servants" in these contexts.
Thus the "sons of God" are not referring to physical offspring. Yes, we are all children of God, but this does not explain why some of God's offspring are being referred to as υἱός (huios) or בֵּן (ben) in Hebrew and some are not.
Again, the answer is that υἱός (huios) in this context is, as the Greek lexicon puts it, "one who depends on another or is his follower." In other words, the "son of God" in this context is a loving servant of God.
Speaking in the third person
This means that while Jesus is certainly including himself as one of God's loving servants, Jesus is not referring to himself as the only loving servant of God. Again this is confirmed when Jesus said:
"Blessed are the peacemakers, for they will be called sons of God.” (Matthew 5:9)By the way, "peacemakers" is derived from the Greek word εἰρηνοποιός (eirēnopoios) which refers to one who brings or spreads peace. In this context, however, it refers to bringing peace to one's heart by spreading God's message. So in this context, Jesus is saying that those who are spreading God's message to others (thereby bringing them internal peace) are God's loving servants.
In fact, Jesus' entire statement above (John 5:18) is referring to activities a loving servant would do. A loving servant is one who willingly, and out of love, follows his master. A loving servant completely relies on his master, and refuses to act alone. He only acts in a way that is pleasing to his master - in this case, the Supreme Being. This is what makes a special loving servant such as Jesus, God's representative.
Here Jesus also clarifies that when the representative of God is acting, he is not acting alone. Because he is only acting on what he knows will please God, he is acting on God's behalf.
This point begins to clarify the issue that had been brought up by those wanting to criticize Jesus, saying that Jesus was putting himself equal to God (John 5:17). Jesus clarified that because he (as God's loving servant and representative) is dedicated and dependent upon God, the actions of God's representative simply reflect God's will.
A loving relationship
This occurs in many loving relationships. A person who loves another will do the will of and act on behalf of the one they love. This is the essence of Jesus' life and the essence of Jesus' relationship with God.
This is important. As Jesus utilizes this metaphor of the relationship between a son and his father, Jesus is revealing an aspect of his intimate loving relationship with the Supreme Being.
Notice also that Jesus says, "Yes, to your amazement..." Why would this be to "your amazement"? Does this mean that everyone else will see what God shows Jesus? And how will they know what God shows Jesus? If Jesus has such an exclusive relationship with God, as sectarian teachings propose, how is it that those who Jesus is talking to will be able to see and be amazed by all the things that God shows Jesus?
The solution to this riddle, and the riddle of why Jesus is talking in the third person, is that Jesus is not speaking of an exclusive relationship between himself and God here. He is speaking in general of the loving relationship between God and his loving servants - comparing to loving sons of fathers.
This is a relationship that Jesus enjoys, and also a relationship that the teachers (prophets) such as John the Baptist, Abraham, Jacob, Solomon, David and many others, also enjoy with God in the spiritual world and as they walked the earth. He is wanting to include his students in this statement as well, because he sees that many of his students are also becoming (or will become) God's loving servants. This is why he can say, "to your amazement..."
Yes, Jesus is trying to teach those around him, who are doubtful that anyone can re-develop our loving relationship with God and become one of God's loving servants. And once they become one of God's loving servants, God will also show them His love through activity and knowledge.
As Jesus indicates, a loving relationship with God is an active relationship. There are two persons involved: The Supreme Being and His loving servant. If one of God's children chooses to become one of God's loving servants, then there is an active relationship. The activity of sharing a relationship is what Jesus is referring to when he says, "shows him all He does."
This is the case in any loving relationship. Each party shows the other their love with activity. Activity illustrates the love that one person feels for another. This type of loving activity also occurs between the Supreme Being and His representative. God is continually showing His loving servants His love through loving activities. And God frequently sends His representatives to teach us - as evidenced by the prophets of the Old Testament.
God's representative is loving God and serving God. This is the relationship that exists between them. We can either see it what it is or try to make Jesus out to be someone he is not.
Jesus came to teach us to love the Supreme Being:
"'Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment." (Matt. 22:37-38)
*Here is the translation of this verse from the Gospels of Jesus:
"Similarly, the Creator loves His Representative and shows him all the things He Himself does. Yes, and He will show him greater deeds than these, and you will marvel." (John 5:20)