Reference for Bava Batra 132:1

והא קיימא לן דרבנן ועוד האמר ר' יוסי בן ר' חנינא בדף של מתכת מחלוקת

But are not all agreed that it was decreed by the Rabbis [on their own authority]? And further, R. Jose son of R. Hanina has said that the dispute [between R. Eliezer and the Rabbis] concerned a board of metal!<span class="x" onmousemove="('comment',' Flat metal articles are susceptible to uncleanness biblically. V. Kel. XI, 1. ');">¹</span>

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