Reference for Niddah 114:39

לא לעולם דארגישה ואימא

Come and hear: If a vestige of blood is found on his rag they are both unclean and are also under the obligation of bringing a sacrifice. If any blood is found on her rag immediately after their intercourse they are both unclean and are also under the obligation of bringing a sacrifice. If, however, any blood is found on her rag after a time they are both unclean by reason of the doubt but exempt from the sacrifice.<span class="x" onmousemove="('comment',' Mishnah supra 14a q.v. notes. ');">³⁵</span>

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