Likutei Moharan 31:16/ליקוטי מוהר"ן ל״א:ט״ז

116. The following relates to what is written above that to be only a scholar is certainly worthless … but one who mistakenly supposes, God forbid, that the quality of scholar-only is the main thing, corresponds to Acher who cut plantings… for it is possible to be a scholar and completely wicked. This has been explained above. And so, because it occasionally happens that even the tzaddik falls from his level—as is known, it is impossible to always stand firm on one level—he may try to strengthen himself by virtue of the level of scholar that he has left. This is not good. Rather, he must strengthen himself with whatever fear of Heaven he has left from the impression that remains [of his previous level].

2Study the Tikkuney Zohar #69 (p.102a): He said to him, “It is written (Genesis 2:17), ‘For on the day that you shall eat from it.’” He said, “On that day he gazed and died.” Rabbi Shimon said, “Because of this it is written, ‘There is a hevel done upon the earth, that there are tzaddikim….’” Study there and understand.