Argument 2: The Oneness of God and the Humanity of Jesus: John 17:3

In John 17:3, Jesus states, "This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent." This verse is pivotal in understanding the distinct roles and natures of God the Father and Jesus Christ. 

Jesus explicitly refers to the Father as "the only true God" and identifies Himself as the one sent by God. This distinction is significant in the context of the verse and the prayer He offers. Jesus does not claim divinity for Himself but acknowledges the Father's unique status as the sole true God. This is consistent with other passages where Jesus speaks of God as someone distinct from Himself, further underscoring His humanity and His role as the messenger and servant of God…

In this solemn prayer, Jesus emphasizes that His mission and the knowledge He imparts are centred on revealing the true nature of God the Father. He indicates that knowing the Father through the teachings and example of Jesus is the path to eternal life. This relationship illustrates that while Jesus operates with divine authority and purpose, He remains a distinct being from the Father, appointed to fulfil a divine mission

From a Unitarian viewpoint, this passage strongly supports the belief that Jesus is a man through whom God's will is enacted, rather than God Himself.

Jesus as a Man: Jesus lived as a human, experiencing human emotions, suffering, and growth. His prayers, particularly in John 17, reflect His deep connection with the Father and His role as an intermediary between God and humanity. This humanity is crucial in understanding Jesus' teachings and His ability to relate to human struggles and experiences.

God as the Sole Creator: The passage reinforces the concept of one true God, separate and distinct from Jesus. This aligns with the Unitarian belief that while Jesus is a central figure in the divine plan, he is not the Supreme Being but rather a distinct entity sent by God to convey His message and guide humanity.

Commentaries on this verse elaborate that the knowledge of God and Jesus is the essence of eternal life. They interpret Jesus' words as emphasizing the necessity of recognizing God as the only true deity and Jesus as the sent one who reveals God's truth to humanity. This interpretation aligns with the Unitarian view that Jesus' divine mission is to make God known, not to claim divinity for Himself​​.

This serves as a strong scriptural basis for the Unitarian belief in the oneness of God and the humanity of Jesus. By clearly distinguishing between God the Father and Jesus, the verse supports the view that while Jesus is divinely appointed and crucial to the understanding of God's will, He is not God Himself but a man to deliver a divine purpose.