Related for Chullin 181:23

רבי יעקב אומר

it follows therefore that he was certain about it.<span class="x" onmousemove="('comment',' For if R. Judah were in doubt as to which was the prohibited thigh the punishment of stripes could not be inflicted at all.');">¹⁴</span>

Maharam Schiff on Chullin