Reference for Yevamot 210:15
מעשה שחלצו כו': בינו לבינה מי ידענא אמר רב יהודה אמר שמואל ועדים רואין אותו מבחוץ
But, surely. R. Nahman had once stated this; for R. Joseph b. Manyumi stated in the name of R. Nahman: The <i>halachah</i> is that<span class="x" onmousemove="('comment',' V. BaH. Cur. edd. omit. ');"><sup>36</sup></span> <i>halizah</i> [must be performed] in the presence of three [judges]!<span class="x" onmousemove="('comment',' Cf. supra 101b. ');"><sup>37</sup></span> — [Both are] required: For if the first only had been stated, it might have been assumed [that three judges are required] ab initio only. but that ex post facto even two [judges are enough] hence we were taught that 'the <i>halachah</i> is not in agreement with this pair'.<span class="x" onmousemove="('comment',' Even ex post facto, which is the case spoken of in our Mishnah, halizah is invalid if no three eligible judges were present. ');"><sup>38</sup></span>