ג מר בריה דרב יוסף משמיה דרבא אמר לומר שממעט בחלק בכורה ואמר מר בריה דרב יוסף משמיה דרבא בן שנולד אחר מיתת האב אינו ממעט בחלק בכורה מאי טעמא (דברים כא, טו) וילדו לו בעינן
3 Mar son of R. Joseph citing Raba explained: This<span class="x" onmousemove="('comment',' The law that A BOY ONE DAY OLD… TRANSMITS. ');"><sup>5</sup></span> means to say that he causes a diminution in the portion of the birthright.<span class="x" onmousemove="('comment',' If, for instance, there were two brothers other than the boy in question, and one of them was the firstborn, the estate is divided, not into three portions (two for the ordinary portions of the two brothers and one for the birthright), but into four portions. Each brother, including the young child, receives one such portion and the firstborn receives the additional fourth portion as his birthright. The firstborn thus receives, as the portion of his birthright, a quarter of the estate, and not (as would have been the case if the child were excluded) a third. ');"><sup>6</sup></span> Mar son of R. Joseph citing Raba further ruled: A son born after the death of his father causes no diminution in the portion of the birthright.<span class="x" onmousemove="('comment',' Though he receives his due portion in the estate. In the case mentioned as an instance in the prev. n. the estate would first be divided into three portions (as if the embryo did not exist) and the firstborn would receive, as his birthright, one of these, which represents a third of the estate. The remaining two thirds would then be divided into three equal shares, each of the three brothers receiving one, I.e., two ninths of the estate. The full portion of the firstborn would accordingly amount to (1/3 + 2/9 = 5/9) five ninths of the estate, while, where the child was one day old, the firstborn's full portion would only amount to half the estate, i.e., (5/9 — 1/2 = 1/18) one eighteenth less. ');"><sup>7</sup></span> What is the reason?<span class="x" onmousemove="('comment',' That a born child does, and an embryo does not cause a diminution in the portion of the birthright. ');"><sup>8</sup></span>