when that man assigns his inheritance to his sons he must not appoint the son of the beloved wife as the firstborn over the son of the unloved wife.
KJV
Then it shall be, when he maketh his sons to inherit [that] which he hath, [that] he may not make the son of the beloved firstborn before the son of the hated, [which is indeed] the firstborn:
ASV
then it shall be, in the day that he causeth his sons to inherit that which he hath, that he may not make the son of the beloved the first-born before the son of the hated, who is the first-born: