Reference for Bava Batra 110:3

שהיה ר"א אומר ספק ביאה טהור ספק מגע טומאה טמא

'If a man goes into a plain<span class="x" onmousemove="('comment',' A stretch of cultivable land divided into fields. ');">⁵</span> in the rainy season where there is known to be uncleanness<span class="x" onmousemove="('comment',' I.e., a grave. ');">⁶</span>

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