Calvin on John 10:27-30

My sheep hear my voice. He proves by an argument drawn from contraries, that they are not sheep, because they do not obey the Gospel. For God effectually calls all whom he has elected, so that the sheep of Christ are proved by their faith. And, indeed, the reason why the name of sheep is applied to believers is, that they surrender themselves to God, to be governed by the hand of the Chief Shepherd, and, laying aside the fierceness of their nature, become mild and teachable. It is no small consolation to faithful teachers, that, though the greater part of the world do not listen to Christ, yet he has his sheep whom he knows, and by whom he is also known Let them do their utmost to bring the whole world into the fold of Christ; but when they do not succeed according to their wish, let them be satisfied with this single consideration, that they who are sheep will be gathered by their agency. The rest has been already explained.

And they shall never perish. It is an inestimable fruit of faith, that Christ bids us be convinced of our security when we are brought by faith into his fold. But we must also observe on what foundation this certainty rests. It is because he will be a faithful guardian of our salvation, for he testifies that our salvation is in his hand And if this were not enough, he says that they will be safely guarded by the power of his Father This is a remarkable passage, by which we are taught that the salvation of all the elect is not less certain than the power of God is invincible. Besides, Christ did not intend to throw this word foolishly into the air, but to give a promise which should remain deeply axed in their minds; and, therefore, we infer that the statement of Christ is intended to show that the elect are absolutely certain of their salvation. We are surrounded, indeed, by powerful adversaries, and so great is our weakness, that we are every moment in imminent danger of death; but as He who keeps what we have committed to him (2 Timothy 1:12) is greater or more powerful than all, we have no reason to tremble as if our life were in danger.

Hence, too, we infer how mad is the confidence of the Papists, which relies on free-will, on their own virtue, and on the merits of their works. Widely different is the manner in which Christ instructs his followers, to remember that, in this world, they may be said to be in the midst of a forest, surrounded by innumerable robbers, and are not only unarmed and exposed as a prey, but are aware that the cause of death is contained in themselves, so that, relying on the guardianship of God alone, they may walk without alarm. In short, our salvation is certain, because it is in the hand of God; for our faith is weak, and we are too prone to waver. But God, who has taken us under his protection, is sufficiently powerful to scatter, with his breath alone, all the forces of our adversaries. It is of great importance for us to turn our eye to this, that the fear of temptations may not dismay us; for Christ even intended to point out the way in which sheep are made to live at ease in the midst of wolves.

And none can wrest them out of my Father's hand. The word and, in this passage, means therefore For, since the power of God is invincible, Christ infers that the salvation of believers is not exposed to the ungovernable passions of their enemies, because, ere they perish, God must be overcome, who has taken them under the protection of his hand.

I and my Father are one. He intended to meet the jeers of the wicked; for they might allege that the power of God did not at all belong to him, so that he could promise to his disciples that it would assuredly protect them. He therefore testifies that his affairs are so closely united to those of the Father, that the Father's assistance will never be withheld from himself and his sheep The ancients made a wrong use of this passage to prove that Christ is (homoousios) of the same essence with the Father. For Christ does not argue about the unity of substance, but about the agreement which he has with the Father, so that whatever is done by Christ will be confirmed by the power of his Father.

Adapted from John Calvin's Commentary on the Bible