Genesis 30:20
And Leah said, God hath endued me with a good dowry; now will my husband dwell with me, because I have born him six sons: and she called his name Zebulun. And Leah said, God hath endued me with a good dowry; now will my husband dwell with me, because I have born him six sons: and she called his name Zebulun.
The birth it records falls between Jacob's night at Bethel in Genesis 28 and his return to the land of Canaan in Genesis 32, while he was in the land of the children of the East at Haran where he served Laban fourteen years for his two daughters. Leah is identified as the mother of six of Jacob's sons, including Zebulun. The birth stands within the account of Jacob's trials and victories extending from Genesis 28 to 32 that result in a complete change of heart, placing Jacob among the Israel of God. It belongs also to the account of Jacob's checkered and unsatisfactory experiences, marked by selfish plotting and the suffering that followed his overreaching.
Genesis 30 displays a patriarchal violation of the marriage institution, and such violations did not lessen marriage's sacred character. They did not diminish its sacred character because marriage was instituted before the fall and its sanctity was not derived from and did not depend on the Decalogue. The birth belongs to the history of Jacob's family which proves that polygamy caused very great unhappiness in every family where it entered.
Polygamy was never anything but evil and wrong, though it was tolerated because of hardness of heart through the whole Old Testament period, and the right standard is the original order in Eden of one husband and one wife. The theory that links Leah's name to wild cow and uses that etymology to claim the tribes shared a bovine totem is speculative and absurd, not a sound explanation of the biblical account of Leah and her sons.