Reference for Bava Batra 131:7

לעולם רבי אליעזר היא ושאני פשוטי כלי עץ דטומאה דרבנן

is fixed in the wall, R. Eliezer says that it is not capable of becoming unclean<span class="x" onmousemove="('comment',' As not being a 'vessel'. ');">⁷</span>

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