דבר חריף וסכין

1) Radish or beets that were cut with a meat knife, used that day or that was not cleaned off are not allowed to be eaten with dairy, until a slice is removed from the location of the cutting that is an "amount to be taken." This amount is equivalent to the width of a thumb. Or let it be tasted, and if it does not have the taste of meat it can be eaten with dairy with mere rinsing. There are those who say that this is also the rule with a knife that was not used that day and was cleaned off. And if you did not take the "amount to be taken" and you did not taste it and you cooked it with Milk, you need 60 times the amount that the knife touched, and this is the rule for something that was cut with a knife of a Non-Jew. Rema: If one cuts [a radish] very finely [i.e., dicing], one needs 60 times against the entire radish.And some say the same is true if it is cut with a meat knife the entire radish is prohibited with dairy. And this is our practice ab initio, however after the fact only an "amount to be taken" is rendered forbidden. And this is only true if the radish itself was cut, but if the radish greens were cut there is no cause for concern. And if there is doubt if the radish was cut with a non-kosher knife, we are lenient. And so too we purchase radishes that were cut on their tops for we can assume they were cut with garden tools.And in a place where only knife-cut radishes can be found, the practice is to permit them through removing an "amount to be taken."

(2) If one cut garlic, onions, kerishin, and tamcha (known as krayn) and other things that are similarly sharp, or pickled fruits, or salted fish, they all have the same laws as one who cuts a radish. Rema: And it is nonetheless permissible to eat spice mixtures made by gentiles like ginger since they use special tools to prepare it our pull it out of the ground without cutting.

§ The mishna teaches: With regard to the knife, one must polish it and it is rendered pure. Rav Ukva bar Ḥama says: And one must thrust it ten times into the ground. Rav Huna, son of Rav Yehoshua, says: And this must be done in untilled earth, i.e., hard earth. Rav Kahana says: And this applies to a good knife that does not have notches, so that the entire surface of the knife is scraped against the ground. This is also taught in a baraita: With regard to a good knife that does not have notches, one can thrust it ten times into the ground. Rav Huna, son of Rav Yehoshua, says: This is sufficient for the purpose of eating cold food with it.

Seif 2 A knife that slaughters in a kosher manner, even though it is dirty with blood is permissible to slaughter again with it. However it is forbidden to cut something hot with it.And it is permissible to cut something cold with it if you rinsed off the blood first.

Seif 3 A knife that slaughtered a trefa, it is forbidden to slaughter with it until it is washed with cold or it is wiped with something hard. The modern custom is to wipe the knife thoroughly on the animal's hair between each slaughtering, and this is proper to do, and if someone slaughters without washing it, we wash off the area of the neck where the slaughter cut. If one finds that he is regularly slaughtering many trefot, we need to stick the knife in hard ground ten times.