ו׳ בטבת ה׳תשע״ט (December 14, 2018)

Hullin 17a-b: Checking the Knife

On previous dapim we have been learning the laws regarding acceptable knives to be used in sheḥita – ritual slaughter. On today’s daf, Rav Ḥisda teaches that the passage in I Shmuel (14:34) should be understood as teaching that the knife that is used for sheḥita must be checked before being used. The Gemara offers a series of different methods that were used to check the knife to be sure that it was not nicked or damaged in a way that would invalidate the slaughter.

  • In the West (i.e. in Israel) the knife was checked in the sun.

Rashi explains this to mean that the knife was checked in clear sunlight, and he brings a second explanation that the knife was held in the sun and its shadow was examined so that any imperfections would be seen.

Rashi brings two explanations for this. According to the first approach, the blade of the knife was moved along the surface of the water and imperfections would show up as a “break” in the water. His second approach suggests that the knife was held with the blade up in the air and water was placed on it. If there was an imperfection, the bead of water would be caught in it and would not make its way to the end of the blade.

  • Rav Sheshet would check the knife on the edge of his tongue.
  • Rav Aḥa bar Ya’akov would check the knife with a strand of hair that he would run along the blade to see if it was caught.
  • In Sura the common expression was that the knife cuts flesh so it should be checked on flesh.
  • Rav Pappa rules that the knife needs to be checked on flesh, on a fingernail and on all three sides (i.e. the blade and 2 sides of the knife). The flesh is similar to the esophagus, while the fingernail is similar to the windpipe. By checking back and forth on each of these on all three edges of the blade we can ensure that the knife will cut both the esophagus and the windpipe cleanly.