Reference for Niddah 29:13

אלא לרב אשי אמאי מטהרי רבנן

the man who had intercourse with her is unclean on account of his contact,<span class="x" onmousemove="('comment',' With the woman. Such a contact with a menstruant within the twenty-four hours' period only subjects him to one day's uncleanness until nightfall and the uncleanness is only Rabbinical and of an uncertain character. ');">¹³</span>

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