Reference for Bekhorot 33:1

היינו דאמר ליה רבן שמעון בן גמליאל

[of offspring in exempting] that is why Rabban Simeon B'Gamaliel said to him: EVEN UNTO TEN GENERATIONS THE OFFSPRING ARE EXEMPT.<span class="x" onmousemove="('comment',' For not only are two generations of offspring exempted but even ten are exempted and even more.');">¹</span>

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