John Calvin on John 6:38

38. For I came down from heaven. This is a confirmation of the preceding statement, that we do not seek Christ in vain. For faith is a work of God, by which he shows that we are his people, and appoints his Son to be the protector of our salvation. Now the Son has no other design than to fulfill the commands of his Father. Consequently, he will never reject those whom his Father hath sent. Hence, finally, it follows, that faith will never be useless. As to the distinction which Christ makes between his own will and the will of the Father, in this respect, he accommodates himself to his hearers, because, as the mind of man is prone to distrust, we are wont to contrive some diversity which produces hesitation. To cut off every pretense for those wicked imaginations, Christ declares, that he has been manifested to the world, in order that he may actually ratify what the Father hath decreed concerning our salvation.