Related for Shabbat 180:5
ר' יהודה אומר אף המוציא כו': ותנא קמא סבר לא מאי טעמא דילמא אכיל ליה אי הכי טהור נמי דהא רב כהנא הוה קאים קמיה דרב והוה קמעבר שושיבא אפומיה אמר ליה שקליה דלא לימרו מיכל קאכיל ליה וקעבר משום (ויקרא יא, מג) בל תשקצו את נפשותיכם אלא דילמא מיית ואכיל ליה ורבי יהודה אי מיית קטן מיספד ספיד ליה:
Abaye observed: And it is found in a palm tree of [only] one covering, and it is prepared [as food] for [acquiring] wisdom; one eats half of its right [side] and half of its left, places it [the rest] in a brass tube and seals it with sixty [i.e., many] seals and suspends it around his left arm; and the token thereof is. A wise man's heart is at his right hand; but a fool's heart is at his left.<span class="x" onmousemove="('comment',' Eccl. X, a fool who has to acquire wisdom has to tie this on his left arm. ');"><sup>9</sup></span> He acquires as much wisdom as he desires, studies as much as he desires, and [then] eats the other half, for if [he does] not, his learning will vanish.<span class="x" onmousemove="('comment',' Lit., 'be eradicated'. ');"><sup>10</sup></span> R. JUDAH SAID: ALSO HE WHO CARRIES OUT, etc. But the first Tanna holds, Not so.<span class="x" onmousemove="('comment',' An unclean locust is not laid aside, etc. ');"><sup>11</sup></span>