פירוש על טהרות 8:8

שהיא קטפרס ([a kneading trough] that lay on an incline/sloping downward) – that one side is low, similar to a slope.

If a kneading trough was sloping downwards and there was dough in the higher part and dripping moisture in the lower part, then three pieces that jointly make up the bulk of an egg cannot be combined together, but two are combined. There is a kneading trough with a sloping side. On the top of the slope, stuck to the sides, are pieces of impure dough. Below them and beneath each piece is some moist liquid. If the dough defiles the moist liquid, then the liquid will defile the trough as well. According to the first opinion, if the dough is in three pieces and together they make up the minimum amount to cause defilement (the bulk of an egg), then they do not join together to defile the liquid. This is because there is not an egg's worth of dough touching any portion of liquid, for each part of the liquid only touches 2/3 of the volume of an egg. However, if there are only two pieces that add up to the volume of an egg, then the pieces do defile the liquid between them because the liquid touches the entire volume of an egg.

משקה טופח מלמטן (running liquid is from below) – on the low side, that is the [unclean] dough that its mixture is soft and its liquid drips, but from above, its mixture is thick and its liquid doesn’t drip.

Rabbi Yose says: the two also cannot be combined unless they compress liquid between them. Rabbi Yose says that for the two pieces of dough to combine they must be pressing the liquid in between them. This means that the liquid is not simply below the pieces of dough, it is right between them, and the dough holds the liquid up, preventing it from flowing to the bottom of the trough.

שלש חתיכות – between the three [pieces of dough] is like an egg’s bulk, one dripping and two that do not drip, they are arranged one next to the other, and the one that drips is below, and now the middle one touches the dripping one and the upper one touches the middle one.

If the liquid was level, even though the piece was the size of a mustard seed they are combined together. If there is liquid simply standing at the bottom of the trough and there is a lot of it, not just moistness on the sides as there is in sections one and two, then even if the pieces are in small crumbs the size of a piece of mustard, they defile the liquid which defiles the trough.

אינן מצטרפות – to be an egg’s bulk to defile the liquid that is flowing from below and the liquid returns and defiles the kneading trough, for contact does not connect the dough unless they stick together as is taught in the Mishnah in the First Chapter [of Tractate Taharot] (Mishnah 7)"מקרצות נושכות זו את זו" /pieces of dough – separated from the main dough in the trough - stick to each other.

Rabbi Dosa says: crumbled food cannot be combined together. Rabbi Dosa says that crumbs don't add up to the requisite amount to transmit impurity. He disagrees only with the opinion in section three, not those in sections one and two.

שתים מצטרפות – if there weren’t other than two pieces of dough, the bottom one that has liquid flowing and the one that is above it that touches it, and if there is between of them an egg’s bulk, they combine to defile the liquid and return and defile the kneading trough.

אפילו שתים אין מצטרפין אא"כ היו רוצצות משקה – always the liquid does not connect until the liquid will be pressing and standing between the two pieces [of dough]. But the Halakha is not according to Rabbi Meir.

ואם היה משקה עומד (and if it was standing liquid) – meaning to say, there wasn’t a sloping/inkling, but rather a cavity for the reception of water/a pond, and the liquid stands between the pieces of dough, even all the measure of an the egg’s bulk that is in the dough are thin crumbs similar to the mustard seed that are separated one from the other, the standing liquid attaches them and combines them to be an egg’s bulk, and defiles the liquid and the liquid returns and defiles the kneading trough.

אוכל פרור – food that is divided into thin crumbs does not combine, for the liquid does not attach them. And the Halakha is not according to Rabbi Dosa.