Reference for Bekhorot 47:17

למאי נפקא מינה למלקא עלה משום אותו ואת בנו

What is the practical differ ence?<span class="x" onmousemove="('comment',' For in either case, if it had given birth previously, whether it is its own offspring or a stranger, it is exempt from the law of the firstling.');">⁹</span>

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