Comentario sobre Shabbat 13:2

שתי בתי נירין – that he put two threads of warp (i.e., longitudinal direction) in the cross beam of the loom which we call “Leitschish.”

Introduction The first part of the mishnah explains the prohibited labor of “making two loops.” The second part deals with sewing.

בנירין – it is explained in the Gemara (Tractate Shabbat 105a) that he extends two times [every] thread of warp in the cross-beam and a third time, he extends on the thread that is joined on to the branch of the reed.

He who makes two loops, on either the cross-pieces [nirim] or one the slips [keros], or in a sifter, sieve, or basket, is liable. We need not fully understand how the ancient loom worked to understand that making two loops, no matter where or how they are done, is considered labor prohibited by the Torah. One is also liable if she makes two loops while weaving a sifter (for sifting flour), a sieve (for separating kernels of grain) or a basket.

בקירוס – a curtain that is woven from the fibrous substance/bast of the palm-tree.

And he who sews two stitches, and he who tears in order to sew two stitches [is liable]. In order to be liable for sewing one needs to sew two stitches. Tearing makes one liable only if the tearing was done with a constructive purpose in mind. If one tears in order to sew up the garment, then one is liable. If the purpose is only destructive, there is no liability.