John Calvin Commentary Genesis 11:30

"And Sarai was barren; She had no child." — Genesis 11:30 (ASV)

But Sarai was barren. Not only does the sacred text state that Abram was without children, but it also provides the reason for this: namely, his wife's sterility. This was to show that her bearing Isaac afterwards was by nothing short of an extraordinary miracle, an event we will explain more fully in its proper place.

Thus, God was pleased to humble his servant, and we cannot doubt that Abram would suffer severe pain from this deprivation. He sees the wicked springing up everywhere, in great numbers, to cover the earth; he alone is deprived of children.

And although until then Abram was ignorant of his own future calling, yet God had designed in Abram's own person, as in a mirror, to make it evident from where and in what manner his Church would arise. For at that time, it lay hidden, like a dry root under the earth.