“Jesus spoke these things; and lifting up His eyes to heaven, He said, “Father, the hour has come; glorify Your Son, that the Son may glorify You, even as You gave Him authority over all flesh, that to all whom You have given Him, He may give eternal life. This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.” John 17:1-3 NASB
From this rich passage, let us briefly observe this: that eternal life is to believe in the only true God, and Jesus Christ Whom He has sent. This knowing is far more than a mere intellectual knowledge, but a relational knowledge; it is not to merely know about the only true God, and Jesus Christ Whom He has sent, but to know Them- both of Them. For we have been told another place, that no one comes to the Father, except through Christ; and so, no one can know the only true God without knowing His Son, and anyone Who knows the Son, shall know the Father, the only true God, through Him.
But it is important for us to observe here one small word, the word “and” in verse three. For the heretics, wanting to deny the existence of the Son by making ‘Son’ merely a another name of mode of the only true God, Whose Son He is, do not believe in the only true God *and* Jesus Christ Whom He has sent, but in a God of their imaginations, Who is Jesus Christ, sent by Himself. But their false teaching is refuted by this one small word; and so all forms of modalism dealt a deathly blow by the clear teaching of scripture here, that the Lord Jesus Christ, the Son of God, is not the only true God Whose Son He is. For if the Son were the only true God, one could not believe in the only true God and in His Son, for believing in one would be to necessarily believe in the other also, if They are the same person, or the same individual being.
But here we read that there is one “only true God”, and this is clearly the very same one that the Lord Jesus Christ calls His Father, in verse one. This is the Supreme Being, the one God, the Almighty, the uncaused Cause of all; and Jesus Christ is not Him, not this one God, but another, a distinct person and a distinct individual being, Who the only true God sent. Not only here is the Lord Jesus Christ distinguished from the only true God by the word “and”; nor only also by the identification of the only true God with His Father, Who He is manifestly distinct from; but also by the fact that He is sent by the only true God, and so is distinguished from Him by that as well, since it is evident that one is sent by another, not by themselves.
Since, then, it is eternal life to know the Father, Who is the only true God, and Jesus Christ His Son Whom He has sent, this cannot be regarded as any minor point of faith, but a very central and important teaching of scripture. For what is more central and foundational than the identity of the only true God? And alongside that, the identity of the Lord Jesus Christ, His Son? And if knowing God and His Son is eternal life, what can be said of those Who do not know, and do not believe, that the only true God is particularly the Father, and the Father the only true God? What life can those Who think that Christ is not sent by the only true God, and is not the Son of the only true God, have? For eternal life is to know the only true God, an Jesus Christ Whom He has sent; and one must doubt that a person knows Them, if he does not even understand their identity, and cannot correctly identify and distinguish one from the other.
Let us then believe the teaching of the Lord Jesus Christ Himself, which is clear: that He is not Himself the only true God, but is another besides Him, sent by Him, His Son. Through this Son, we know the only true God, His Father; and if we deny these teachings, we deny the teaching of the Lord Himself, and deny ourselves of eternal life.