663. Tearing

Shabbos 10:9

One who sews two stitches is liable as long as he ties them at both ends so that they remain in place without slipping out. If a person sews one more stitch, he is liable even if he did not tie the ends because then the stitches will remain in place. One who pulls a sewing thread taut on the Shabbos is liable because this is a necessary component of sewing.

Shabbos 10:10

One who tears enough fabric to tie two stitches in order to tie two stitches is liable; if he tears with purely destructive intent, he is not liable. If a person tears in anger or in mourning for a deceased relative for whom one is required to tear his garments, he is liable. This is because by tearing, he settles his mind and calms himself. Since his anger is assuaged by this action, it is considered a constructive act for which one is liable. One is liable for opening a neck hole in a garment on Shabbos.