John Calvin Commentary John 17:8

"for the words which thou gavest me I have given unto them; and they received [them], and knew of a truth that I came forth from thee, and they believed that thou didst send me." — John 17:8 (ASV)

And they have received them. He expresses the manner of this knowledge. It is because they have received the doctrine which he taught them. But so that no one may think that his doctrine is human or is earthly in its origin, he declares that God is the Author of it, when he says, The words which you gave me I have given to them.

He speaks according to his ordinary custom, in the person of the Mediator or servant of God, when he says that he taught nothing but what he had received from the Father. For since his own condition was still humble while he was in the flesh, and since his Divine majesty was concealed under the form of a servant, by 'the Father' he simply means God.

Yet we must adhere to the statement which John made at the beginning of his Gospel that, insofar as Christ was the Eternal Word of God, he was always one God with the Father. The meaning therefore is that Christ was a faithful witness of God to the disciples, so that their faith was founded exclusively on the truth of God, since the Father himself spoke in the Son. The receiving, of which he speaks, arose from his having efficaciously manifested to them the name of his Father by the Holy Spirit.

And have known truly. He now repeats in other words what he had previously mentioned; for that Christ came out from the Father, and was sent by him, has the same meaning as what was said before, that all things which he has are from the Father. The meaning amounts to this, that faith should cast its eyes directly on Christ, yet so as to form no conception of him that is earthly or lowly, but to be carried upwards to his Divine power, so as to believe firmly that he has perfectly in himself God, and all that belongs to God.

And have believed. Let it be observed, also, that in the previous clause he uses the verb 'know,' and now he uses the verb 'believe'; for thus he shows that nothing which relates to God can be known correctly except by faith, but that in faith there is such certainty that it is justly called knowledge.