“Suppose a man has two wives—the one loved and the other unloved—and both the loved and the unloved bear him sons. But it happens that the firstborn son belongs to the unloved wife.
Then she became pregnant again and gave birth to a son, and said, “For Adonai heard that I am hated, so He’s given me this one also,” and she named him Simeon.
Now on the day he lets his sons inherit what he has, he must not treat the loved one’s son as firstborn, in place of the unloved one’s son, who is the firstborn.