Reference for Shabbat 213:4

<br><br><big><strong>הדרן עלך האורג</strong></big><br><br>

And the third: If one catches a snake on the Sabbath: if he is engaged therewith [sc. in catching it] so that it should not bite him,<span class="x" onmousemove="('comment',' 'Mith'assek' may be understood in the sense of performing indirect labour, i.e., he catches it only incidentally, as he does not need the snake but merely desires to prevent it from dong harm. ');">⁶</span> he is exempt; if for a remedy,<span class="x" onmousemove="('comment',' The snake's poison can be used medicinally. ');">⁷</span>

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