John Gill

And now I have told you before it came to pass,.... This is a strong proof of his true and proper deity, for none but the omniscient God can tell of things before they come to pass; this is peculiar to him, and distinguishes him from the gods of the Gentiles; see Isa 41:22; that when it is come to pass, ye might believe: that is, that when he was removed from them, and gone to his Father, they might then believe that he was truly God, the Son of God, the promised Messiah; and that he was then in glory, and at the right hand of God.