Reference for Shabbat 5:1

בבא דרישא פטור ומותר לא קתני אלא בבא דסיפא דפטור אבל אסור קשיא

he does not teach what involves no liability and is [also] permitted.<span class="x" onmousemove="('comment',' E.g., if the man without extends his hand and places an article into the hand of the man within, the latter commits no action at all, being passive throughout, and, as far as the Sabbath is concerned, he does nothing forbidden. ');">¹</span> But the last clause, where no liability is involved, yet it is forbidden, is indeed difficult.<span class="x" onmousemove="('comment',' Why these are not counted as separate actions, as explained in n. 4. ');">²</span>

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