Likutei Moharan 54:13/ליקוטי מוהר"ן נ״ד:י״ג

113. The general principle is that which our Sages of blessed memory said: A person should not deduce a gezerah shavah -parallel of his own (Pesachim 66a). For a person might deduce his own parallel and it can stem from the imagination, because he is medameh (likens) one thing to another, as explained above. See there.

2It is therefore forbidden for a person to deduce his own parallel—i.e., to liken one thing to another—unless he received it from his teacher, who received it from his teacher, back to Moshe Rabbeinu, of blessed memory, directly from the Almighty—in order to be spared from the imagination. Understand this.