Mishnayos Challah Perek 2 Mishnah 6

חמשת רבעים – of Kab are liable for Hallah, as it is written (Numbers 15:20): “As the first yield [of your baking, you shall set aside a loaf as a gift…],” and the flour of the wilderness was the quantity of grain in a sheaf as a capitation tax, and the Omer is one-tenth of an Ephah. The Ephah is three Seah, and the Seah is six Kabim; hence we have eighteen Kabim in an Ephah, and the Kab is four Logs; which are seventy-two Logs. A tenth of seventy is seen Logim and the tenth of two Logim is an egg’s bulk and one-fifth of an egg, for the Log is [equivalent to] six eggs. When they came to Jerusalem and they added one-sixth on the measurements, it was found that six Logim were five, and the seenth Log was five eggs. For every six became five, and an egg and the fifth of an egg became an egg. It was found that the Omer that was in the wilderness was seven Logim and an egg and one-fifth of an egg. But in Jerusalem it became six logim. When they came to Sephhoris, and they added one-sixth on he measurements of Jerusalem, so that the six Logim became five, and that is equal to the five-fourths of flour. And the Logim were called fourths, because the Log was one-fourth of a Kab, for a Kab was four Logim.

הן ושאורן – the leaven that they put into it.

וסובן – which is thin

מורסנן – that is thick – all of which combines with the flour to complete the measurement, for a poor person who eats his bread combined with flour combined with bran flour and coarse flour.

ניטל מורסנן מתוכן חוזר לתוכו הרי אלו פטורין – for it is not the manner of dough to restore the coarse bran into it after he took it from there.