Tosefta for Bava Batra 246:6
כיצד הניח להן אביהן פרה מוחכרת ומושכרת ביד אחרים או שהיתה רועה באפר וילדה בכור נוטל פי שנים אבל בנו בתים ונטעו כרמים אין בכור נוטל פי שנים
— Rabbah b. Shila replied; Ishi descended from the sons of Manasseh, for it is written, And the sons of Manasseh were Hepher and Ishi.<span class="x" onmousemove="('comment',' This quotation does not occur in our Bible text. The nearest approach is I Chron. V, 24, 'And these were the heads of their father's houses, Epher and Ishi'. ');"><sup>15</sup></span> Our Rabbis taught: The firstborn son [of a priest] takes a double portion in the shoulder, and the [two] cheeks, and the maw,<span class="x" onmousemove="('comment',' The priests' due from people who offer sacrifices. V., Deut. XVIII, 3. ');"><sup>16</sup></span> in consecrated objects and in the [natural] appreciation of an estate that accrued after the death of the father.<span class="x" onmousemove="('comment',' Of the heirs. ');"><sup>17</sup></span>