Reference for Niddah 120:37

בשלמא התם אימר שמש עכביה לדם [אבל] הכא אם איתא דהוי דם מאן עכביה

He is of the same opinion as Bar Pada who laid down: Whenever her husband is liable to a sin-offering,<span class="x" onmousemove="('comment',' In the case, for instance, where she discovered menstrual blood immediately after their intercourse, when it is assumed that the discharge had occurred during intercourse. ');">³⁵</span>

Jastrow

Jastrow