Torah from the Tzaddik

קל"ה - הלכות ברכת התורה א:ב

A person must travel to the Tzaddik to hear words of Torah directly from his lips, because then one is able to receive the light of the Torah, which is a blessing and an elixir.  But even if one does hear words of Torah from the true Tzaddik, he is unable to fully receive these words except through guarding his bris.

Kabbalas HaTorah

קל"ה - הלכות ברכת התורה א:א

By going out from the Exile of Egypt, which is the nakedness of the land and a concept of sexual immorality, and sanctifying ourselves in the 49 days of Sefiras HaOmer, which encompasses all the letters in the names of the Tribes, which is a concept of "the holiness of one's bris or covenant," one can merit to receive the Torah on Shavuos.  The whole purpose of receiving the Torah is that it [Torah] should be a blessing and an elixir.  This can only be done through  the holiness of one's bris.