What does Genesis 29:31 mean?

First Laban and then the Lord Himself intervened on behalf of poor, heartbroken Leah. It's easy to imagine that she might have grown in affection for Jacob during the seven years in which he was working for Laban. Unfortunately for Leah, those years were worked by Jacob specifically to earn Rachel's hand in marriage. It's also easy to understand the hurt she may have felt that her younger, more attractive sister would be married before she was (Genesis 29:16–20). Whether in sympathy for his daughter's plight, or simply as an act of greed, Laban used an outrageous act of cruel deception, tricking Jacob into legally marrying Leah first (Genesis 29:21–26).

Jacob accepted the marriage, but unsurprisingly did not feel the same love for Leah which he carried for Rachel. Jacob loved Rachel enough to work seven years for her; finding Leah in his marriage bed was a cruel surprise. The previous verse tells us flatly that he loved Rachel more than Leah. This verse goes further: Leah was hated. This is a common feature of ancient literature, which often used exaggerated contrasts in order to show a difference from one side to another. Jacob's love for Rachel, combined with his resentful indifference to Leah, meant she was "hated," at least by comparison. Then again, in this particular case, Jacob's experience might well have caused him to hate Leah, literally.

Now God, who is always with Jacob as He has promised, takes particular notice of Leah's great pain. To comfort her, the Lord causes her to become pregnant, while the favored, more beautiful, and younger Rachel remains childless.

Rachel becomes the third wife of the first patriarchs of Israel unable to conceive a child until the Lord allows it. The same was true for Sarah (Genesis 16:1–2) and Rebekah (Genesis 25:21). Even Leah's firstborn son by Jacob is only born with the Lord's intervention. Clearly, it was important to God for Israel to know that children were a gift from Him and that pregnancy was not something that could be controlled by human will alone.