John Calvin Commentary Genesis 29:31

"And Jehovah saw that Leah was hated, and he opened her womb. But Rachel was barren." — Genesis 29:31 (ASV)

And when the Lord saw. Moses here shows that Jacob’s extravagant love was corrected by the Lord, just as the affections of the faithful, when they become excessive, are usually tamed by the rod. Rachel is loved, not without wrong to her sister, to whom due honor is not given.

The Lord, therefore, intervenes as her vindicator and, by a suitable remedy, turns Jacob’s mind in that direction to which he had been most averse. This passage teaches us that offspring is a special gift of God, since the power of making one fertile and of cursing the womb of the other with barrenness is expressly ascribed to Him.

We must observe further that the bringing forth of offspring tends to reconcile husbands to their wives. This is why the ancients also called children pledges, because they contribute significantly to increasing and cherishing mutual love. When Moses asserts that Leah was hated, his meaning is that she was not loved as much as she should have been.

For she was not intolerable to Jacob, nor did he pursue her with hatred. Instead, Moses, by using this word, amplifies Jacob's fault in not having discharged his duty as a husband and in not having treated her, his first wife, with adequate kindness and honor.

It is important to note this carefully, because many think they fulfill their duty if they do not break out into mortal hatred. But we see that the Holy Spirit pronounces those as hated who are not sufficiently loved; and we know that human beings were created for this purpose: that they should love one another. Therefore, no one will be counted guiltless of the crime of hatred before God except the one who embraces his neighbors with love.

For not only will secret displeasure be considered hatred, but also the neglect of our brothers and sisters and the cold charity that always prevails in the world. The more closely anyone is connected with another, the greater must be the effort to adhere to each other in a more sacred bond of affection. Moreover, regarding married persons, even if they do not openly disagree, yet if they are cold in their affection towards each other, this aversion is not far removed from hatred.