Let us endeavor to discern from the Scriptures and from reason the equality of the first and second persons of the Holy Trinity and examine how Jesus can be both equal to the Father and lesser than the Father in the oneness of the Trinity. There are many errors by the heretics in the understanding of Jesus as He related to His divine atoning work of salvation. Man’s desire to be exalted to being divine prompts many to try to explain in terms understood within the limits of our intellect the mysterious aspects of God. Most often man fails in this endeavor and concludes errors to be fact by failing to recognize his intellectual inferiority to the mind of God.
The incarnation being for the purpose of working out the salvation of humanity required Jesus to be the one mediator between God and man and in Scriptures there are indications that the Father is greater than the Son. This must be balanced with the fact that Jesus is also less than himself after the incarnation as is the nature of the flesh but the Scriptures clearly tell us of the fact that before the incarnation that He was eternal and after His atoning work His eternal substance remains. Jesus himself reveals and is quoted as saying that the Father is greater than I. Jesus at the incarnation was made less than Himself as being a servant instead of one who is served as is God. We find by Scriptures that Jesus is greater than Himself as God and lesser than Himself as a servant. Neither of these two roles as servant or as God are denied in Scriptures instead they reveal that Jesus is equal to the Father and also that the Father is greater than the Son.
Philippians 2:7 (King James Version)
7But made himself of no reputation, and took upon him the form of a servant, and was made in the likeness of men:
In the form of God Jesus is the Word made flesh but in the form of the servant He came forth from a woman under the same law as man to fulfill the law and serving within the law to redeem mankind from the law. He is the only perfect sacrifice that could accomplish the atoning work in that His perfection was not from being under the law but by being truly God. Just as God was not changed to be the servant so too the servant was not changed to be God. Man was not made without the Son and to say differently is to deny Scriptures that say:
Genesis 1:26 (King James Version)
26And God said, Let us make man in our image, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth.
It is clear that in the form of the servant of man Jesus was fully God in every sense. As the servant He was fully man in every sense. Neither the servant nor God changed into the other but both remained fully God and fully man in every aspect of reason. God bless!