ל"ה -חלכות כבוד רבו ותלמיד חכם ג:יח
It is forbidden to derive material pleasure from the Channukah lights. The holiday of Channukah was instituted by Chazal, and the lights of Channukah correspond to the true tzaddikim. The implication is that one should not seek the light of the tzaddik for material benefit, as it is common in our generation. Rather, one must attach oneself to the tzaddikim for spiritual purposes only.