Eruvin 36a-37a
Questionable eruvin: If, how, and when they are effective • Retroactive eruvin • Justification for setting up eruvei techumin: why run away from the chazzan?
Questionable eruvin: If, how, and when they are effective • Retroactive eruvin • Justification for setting up eruvei techumin: why run away from the chazzan?