Reference for Yoma 91:13

ולרב חסדא קשיא מאי שנא שבת דכתי' במועדו אפי' בשבת טומאה נמי במועדו ואפי' בטומאה

Because Scripture said: In its due season<span class="x" onmousemove="('comment',' Num. XXVIII, 2.');">¹⁰</span> i.e., even in levitical uncleanness, [it should suspend also] the Sabbath, [since] 'in its due season' [implies] even on the Sabbath? - And according to R'Hisda there is a difficulty.

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