Reference for Eruvin 206:11
ותיפוק ליה משום חציצה בשמאל
one can easily see why removal with the hand was forbidden as a preventive measure against the use of an instrument,<span class="x" onmousemove="('comment',' As a change is made from a Pentateuchal prohibition to a shebuth (though either might be equally superseded) so must a change be made from the major shebuth (removal with the hand) to the minor one (removal with a friend's teeth which is less usual than that with the hand) .');"><sup>35</sup></span> but if you maintain that it represents the view of the Rabbis,<span class="x" onmousemove="('comment',' The reason for whose ruling is not the desirability for a change but the view that only a Shebuth may be superseded but not a Pentateuchal prohibition.');"><sup>36</sup></span> why should he not be allowed to remove it with his hand?<span class="x" onmousemove="('comment',' Which is no less a Shebuth than removal with the teeth.');"><sup>37</sup></span> And nothing more need be said about the matter.<span class="x" onmousemove="('comment',' Since it is quite evident that the view represented is that of R. Eliezer.');"><sup>38</sup></span>