Genesis 17:4

4.As for me, behold, my covenant is with thee (404) They who translate the passage, ‘Behold, I make a covenant with thee,’ or, ‘Behold, I and my covenant with thee;’ do not seem to me faithfully to represent the meaning of Moses. For, first, God declares that he is the speaker, in order that absolute authority may appear in his words. For since our faith can rest on no other foundation than his eternal veracity, it becomes, above all things, necessary for us to be informed that what is proposed to us, has proceeded from his sacred mouth. Therefore, the pronoun I, is to be read separately as a preface to the rest; in order that Abram might have a composed mind, and might engage, without hesitation, in the proposed covenant. Whence a useful doctrine is deduced, that faith necessarily has reference to God: because, although all angels and men should speak to us, never would their authority appear sufficiently great to confirm our minds. And it cannot but be, that we should at times waver, until that voice sounds from heaven, ‘I am.’ Whence also it appears what kind of religion is that of the Papacy: where, instead of the word of God, the fictions of men are alone the subject of boast. And they are justly exposed to continual fluctuation, who, depending upon the word of men, act unjustly towards God, by ascribing to them more than is right. But let us have no other foundation of our faith than this word ‘I’, not as spoken indifferently by any mouth whatever, but by the mouth of God alone. If, however, myriads of men set themselves in opposition, and proudly exclaim, ‘We, we,’ let this single word of God suffice to dissipate the empty sound of multitudes.

And thou shalt be a father of many nations (405) It is asked what is this multitude of nations? It obviously appears, that different nations had their origin from the holy Patriarch: for Ishmael grew to a great people: the Idumeans, from another branch were spread far and wide; large families also sprung from other sons, whom he had by Keturah. But Moses looked still further, because, indeed, the Gentiles were to be, by faith, inserted into the stock of Abram, although not descended from him according to the flesh: of which fact Paul is to us a faithful interpreter and witness. For he does not gather together the Arabians, Idumeans, and others, for the purpose of making Abram the father of many nations; but he so extends the name of father, as to make it applicable to the whole world, in order that the Gentiles, in other respects strangers, and separated from each other, might, from all sides combine in one family of Abram. I grant, indeed, that, for a time, the twelve tribes were as so many nations; but only in order to form a prelude to that immense multitude, which, at length, is collected together as the one family of Abram. And that Moses speaks of those sons, who, being regenerate by faith, acquire the name, and pass over into the stock of Abram, is sufficiently proved by this one consideration. For the carnal race of Abram could not be divided into different nations, without causing those who had departed from the unity, to be immediately accounted strangers. Thus the Church rejected the Ishmaelites, the Idumeans, and others, and regarded them as foreigners. Abram therefore was not called the father of many nations, because his seed was to be divided into many nations; but rather, because many nations were to be gathered together unto him. A change also of his name is added as a token. For he begins to be called Abraham, in order that the name itself may teach him, that he should not be the father of one family only; but that a progeny should rise up to him from an immense multitude, beyond the common course of nature. For this reason, the Lord so often renews this promise; because the very repetition of it shows that no common blessing was promised.