If a man has two wives, the one beloved and the one hated, and they bear him sons, the beloved and the hated, and the firstborn son is the hated one’s—
English: “And they bear” — this teaches that a fetus does not reduce the firstborn’s double portion. Why? Because it is written “and they bear” (already born).
On the daf / in context: The double portion is calculated only among sons already born at the father’s death. A fetus in the womb does not share in reducing the firstborn’s share of the bechorah, though it does share in the ordinary portion once born.
Type of Learning
Derash on the perfect tense “ve-yaledu.”
What Is Learned
A fetus does not diminish the firstborn’s double portion; the bechorah is calculated among sons already born.