John Calvin Commentary Genesis 9:12

"And God said, This is the token of the covenant which I make between me and you and every living creature that is with you, for perpetual generations:" — Genesis 9:12 (ASV)

This is the token of the covenant. A sign is added to the promise, in which the wonderful kindness of God is exhibited, who, for the purpose of confirming our faith in his word, does not disdain to use such helps. And although we have more fully discussed the use of signs in Genesis 2:1, we must briefly maintain from these words of Moses that it is wrong to sever signs from the word.

By the word, I mean not that of which Papists boast, by which they enchant bread, wine, water, and oil with their magical whisperings, but that which may strengthen faith: just as the Lord here plainly addresses holy Noah and his sons; he then adds a seal for the sake of assurance.

Therefore, if the sacrament is wrested from the word, it ceases to be what it is called. It must, I say, be a vocal sign, so that it may retain its force and not degenerate from its nature. And not only is that administration of sacraments in which the word of God is silent vain and ludicrous, but it brings with it pure satanic delusions.

From this we also infer that from the beginning, it was the distinctive property of sacraments to serve for the confirmation of faith. For certainly, the covenant includes the promise to which faith ought to respond. To some, it appears absurd that faith should be sustained by such helps.

But those who speak this way do not, in the first place, reflect on the great ignorance and weakness of our minds; nor do they, secondly, ascribe due praise to the working of the secret power of the Spirit. It is the work of God alone to begin and to perfect faith, but he does it by such instruments as he sees fit; the free choice of which is in his own power.