3. this is--that.
      life eternal, that they might--may.
      know, &c.--This life eternal, then, is not mere conscious and unending existence, but a life of acquaintance with God in Christ (Job 22:21).
      thee, the only true God--the sole personal living God; in glorious contrast equally with heathen polytheism, philosophic naturalism, and mystic pantheism.
      and JesusChrist whom thou hast sent--This is the only place where our Lord gives Himself this compound name, afterwards so current in apostolic preaching and writing. Here the terms are used in their strict signification--"JESUS," because He "saves His people from their sins"; "CHRIST," as anointed with the measureless fulness of the Holy Ghost for the exercise of His saving offices (see on Mt 1:16); "WHOM THOU HAST SENT," in the plenitude of Divine Authority and Power, to save. "The very juxtaposition here of Jesus Christ with the Father is a proof, by implication, of our Lord's Godhead. The knowledge of God and a creature could not be eternal life, and such an association of the one with the other would be inconceivable" [ALFORD].

JFB.