Reference for Niddah 73:10

א"ל אביי

also is a cause of the uncleanness of <i>zibah</i>, for we have learnt: If he observed a first discharge he must be examined, if he observed a second discharge he must be examined, but if he observed a third he need not be examined.<span class="x" onmousemove="('comment',' Zabim II, 2. Thus it is shown that a third discharge, even if it was due to an accident, provided the first two discharges were not due to such a cause, renders a person a confirmed or major zab. ');">⁹</span>

Jastrow

Jastrow