Reference for Shabbat 209:15
והקורע ע"מ לתפור שתי תפירות: היכי משכחת לה
HE WHO MAKES TWO MESHES, ATTACHING THEM EITHER TO THE CROSS-PIECES [NIRIM]. What does, 'TO THE NIRIM' mean? — Said Abaye: Two in a mesh and one in the cross-piece. OR TO THE SLIPS [KEROS]. What is KEROS? — Said Rab: The slips.<span class="x" onmousemove="('comment',' Jast.: the thrums or slips to which the threads of the warp are attached. ');"><sup>23</sup></span> AND HE WHO SEWS TWO STITCHES. But we have [already] learnt it in [the list of] principal labours: 'and he who sews two stitches?<span class="x" onmousemove="('comment',' Supra 73a. ');"><sup>24</sup></span> — Because he wishes to teach the second clause: AND HE WHO TEARS IN ORDER TO SEW TWO STITCHES, he also teaches, AND HE WHO SEWS, [etc.]. But we learnt about tearing too in [the list of] principal labours? Rather because he wishes to teach in a subsequent clause, 'He who tears in his anger or for his dead',<span class="x" onmousemove="('comment',' Infra b. ');"><sup>25</sup></span> he therefore teaches [here], HE WHO SEWS TWO STITCHES. AND HE WHO TEARS IN ORDER TO SEW TWO STITCHES. How is that possible?