John Calvin Commentary Isaiah 44:21

"Remember these things, O Jacob, and Israel; for thou art my servant: I have formed thee; thou art my servant: O Israel, thou shalt not be forgotten of me." — Isaiah 44:21 (ASV)

Remember these things, O Jacob. He now applies for the benefit of the people what he had so often said about the superstitions and falsehoods of the Gentiles, by which people who are not well instructed are deceived in the worship of God. Nor does he write these things only for the people of his own age, but primarily for their posterity, who were to be carried away to Babylon, and might have been corrupted by prolonged contact with the Babylonians, and drawn aside from the true worship of God, if the Lord had not placed those restraints on them. Therefore, the Prophet exhorts them, while they were held captive, to remember those exhortations and through them to strengthen their hearts amid those grievous calamities.

For you are my servant. I have formed you. He adds this reason why they ought to remember these promises and to beware of the general contagion of other people; for it would have been intolerable for the elect people, whom God had surrounded with the barriers of His Law, so that they might be separated from others, to freely and indiscriminately mingle with the pollutions of the Gentiles. As if he had said, “It is not wonderful that the Babylonians should wander in their errors, but you ought to be unlike them; for ‘I have formed you,’ that you might ‘serve me;’ I have regenerated and sanctified you, that you might be an heir of eternal life.”

Of this creation we have explained extensively on previous occasions, that it relates to the renewal of the soul. Scripture frequently employs this argument: You have been called to sanctification and not to uncleanness (1 Thessalonians 4:7), Walk as the children of light (Ephesians 5:8) in the midst of a crooked and perverse nation (Philippians 2:15), and in other passages of the same kind.

From this we ought to infer that we will be doubly punished if it is found that we have quenched by neglect or indifference the light with which the Lord has enlightened us. For our criminality will be far greater than that of others on whom He has not bestowed a similar favor. Heathens will indeed be punished, and no excuse of ignorance will be of any avail to them; but far heavier will be the punishment of those who will abuse the grace of God.

Do not you forget me. He means that it is impossible for anyone who has once entered the right path to be led away from it, if they are not guilty of forgetting God; for error and delusions can never prevail as long as the remembrance of God is rooted in our hearts.

Therefore, let everyone who turns away from God and falls into superstition and impiety lay the blame on his own wickedness. Thus, we ought to observe carefully the cause of apostasy—that is, forgetfulness of God—which gradually withdraws us from the right path until we leave it altogether.

Besides, he reminds them that by this remedy they will be secure against rebellion, if they engage in constant meditation; for our minds, through their sluggishness, easily contract rust, so to speak, which infects and corrupts all knowledge of God until it is entirely destroyed.