The Gospel of John is used, or I should say misused, to “prove” Jesus is God! Yet, ironically, the gospel is primarily defined by Father–Son language (denoting the subordination of the Son) and by the principle known as agency!

According to the TDNT article on the word apostolos: The Rabbis summed up this basis of the shaliach [Heb. agent] in the frequently quoted statement: “the one sent by a man is as the man himself” (Bet., 5, 5). That is, the shaliach [the agent] is as good as the sender in all that he says and does in execution of his commission.

The noted British theologian and minister G.B. Caird concluded that “This practice of treating the agent as though he were the principal is of the greatest importance for New Testament Christology.” The Language and Imagery of the Bible, 1988, p. 181

Jesus repeatedly relies on the principle of agency in verses like John 12:44: “He who believes in me, believes not in me but in him who sent me.”

And in John 13:2: “Very truly I tell you, whoever accepts anyone I send accepts me; and whoever accepts me accepts the one who sent me.”

Peter Borgen, in his often cited article GOD’S AGENT IN THE FOURTH GOSPEL, notes that this “saying is a very close parallel to the saying by the king in the quotation from Siphre [an ancient Jewish midrash]: You have not spoken concerning my servant but concerning me.

The Oxford Handbook of the Reception History of the Bible (2013) adds:

“The repeated stress, in these and other passages, on the `sending’ of Jesus (e.g. 5:23-4, 36-7; 7:29; 10:36; 17:18) indicates that his depiction as God’s authorized envoy is to be explained against the background of Jewish notions of agency. Based on the principle that the one who is sent (Hebrew: shaliach) is endowed with the full authority of the sender….Jesus, therefore, functions as the unique emissary, because the Father ‘has placed all things in his hands’ (3:35). His words and works are those of God, including the giving of life and executing judgement (5:21-2, 27). The Son acts in dependence upon the one who sent him (7:28; 8:42; 10:37; 12:49) and commits himself obediently to the will of the Father (4:34; cf. 5:30; 6:38). During his earthly life he speaks and acts in unity with God (10:30), so that to see and know him is to see and know the Father (12:45; 14:7, 9).