John Calvin Commentary Genesis 13:16

"And I will make thy seed as the dust of the earth: So that if a man can number the dust of the earth, then may thy seed also be numbered." — Genesis 13:16 (ASV)

And I will make thy seed as the dust. Omitting those subtleties by which others argue about nothing, I simply explain the words to mean that the seed of Abram is compared to the dust because of its immense multitude; and truly, the sense of the term is to be found only in Moses’ own words.

It was, however, necessary to add here that God would raise up a seed for him, of which he was until now destitute. And we see that God always keeps him under the restraint of his own word and intends for him to be dependent upon his own lips. Abram is commanded to look at the dust; but when he turns his eyes to his own family, what likeness is there between his solitude and the countless particles of dust?

Therefore, the Lord requires us to attribute this authority to his own word: that it alone should be sufficient for us. It may also give occasion for ridicule that God commands Abram to travel until he had examined the whole land. For what purpose should he do this, except that he may more clearly perceive himself to be a stranger, and that, being exhausted by continual and fruitless restlessness, he may despair of any stable and permanent possession?

For how can he persuade himself that he is lord of that land in which he is scarcely permitted to drink water, even though he has dug the wells with great labor? But these are the exercises of faith, so that it may perceive in the word those things which are far off and hidden from the physical senses. For faith is the beholding of absent things (Hebrews 11:1), and it has the word as a mirror in which it may discover the hidden grace of God.

And the condition of the pious in these days is not dissimilar. For since they are hated by all, are exposed to contempt and reproach, wander without a home, are sometimes driven here and there, and suffer from nakedness and poverty, it is nevertheless their duty to take hold of the inheritance that is promised. Let us therefore walk through the world as people denied all rest, who have no other resource than the mirror of the word.