R' Zev Sero asked:<br><She'elas tam: Who, exactly, "instituted" this? Where, and how long ago?<br><br>It is a Gemara in Shabbos 21b, the Gemara states "mitzva l'hanicha al pesach beiso mibachutz ... u'bisha'as hasacana manicho al shulchano v'dayo
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