Tearing, the av melachah of koraya, is forbidden on Shabbat. As will be discussed below, koraya in the Mishkan was actually part of the sewing process. As such, the av melachah refers to tearing with the intention to resew the tear using at least two stitches.1 Koraya does not only apply to woven materials; any two items attached to each other in a permanent way can be subject to koraya if they are torn apart with the intention to reattach them more tightly.2 These actions, however, would only be considered toldot of koraya, because they differ from the way koraya was done in the Mishkan.

Koraya in the Mishkan

The roof of the Mishkan was made from tapestries that were sewn together. Occasionally, these tapestries would tear and in the process of sewing them back together the tear needed to be widened to make for a straight and even seam.3 This tearing is the source for the melachah of koraya.

Some authorities maintain that koraya involves any tearing done for a useful purpose, even if the tear will not be resewn.4 For example, tearing off a piece of silver foil from a roll in order to wrap food. Additionally, they say that koraya also includes tearing one whole thing into two, and is not restricted to detaching two things that were previously attached as was the case in the Mishkan.5

The Alter Rebbe disagrees with both of these points. He follows the view of Tosafot6 and Ritva7 who maintain that only tearing with the intention to reattach falls under the prohibition of koraya. Other tearing is only rabbinically prohibited.8 He also says that tearing one whole thing into two is not included in the melachah at all; only tearing apart two items that were previously attached.9

This clarifies a number of issues that are frequently misunderstood. Most people assume the reason toilet paper should not be used on Shabbat is because tearing it would be a transgression of koraya. However, from what we have learned it emerges that according to the Alter Rebbe, there is no issue of koraya at all with toilet paper, because the roll is one whole and koraya does not apply to tearing a whole into two (or more). Rather, tearing toilet paper to a specific size, usually by tearing it on the perforated line, is forbidden under a separate melachah of mechateich, cutting. If one is not particular about the size of the piece he is cutting it is also forbidden due to the issue of tikkun kli - making something more usable on Shabbat. Another action people mistakenly attribute to koraya is tearing open candy bars or packets of coffee or sugar. While doing so on Shabbat is indeed tricky, and certain halachic considerations must be adhered to, koraya is often not one of them.