זוהר ויקרא — דף לט ע”א

Aaron took Elisheva in order to perfume her, gladden her, and unite her with the King in a perfect union, so that blessings would be found through him for all the worlds. Therefore the priest must display a radiant face and joy, and for this reason judgment, anger, and sadness are kept far from him. This is why "your brothers, the whole house of Israel, shall bewail the burning," and not the priest, of whom it is said "you shall drink no wine nor strong drink, you and your sons with you."<br />
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It is explained that "the beginning of wine is joy, and its end is sadness," and that wine comes from the side of the Levites, while the priest's side consists of clear and shining waters.<br />
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Wine, oil, and water came out from one place: oil and water go to the right, taken by the priests, and oil is always discreet, coming from the side of thought, which cannot be heard. Wine, by contrast, which comes to raise the voice and never falls silent, is inherited by the Levites on the left side, and stands in judgment, as it is written, "and by their word shall every dispute and every affliction be settled." Therefore, when the priest enters the Sanctuary for his service, he is forbidden to drink wine, since his deeds are secret and hidden, whereas wine reveals secrets.<br />
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It is told that Rabbi Yehuda and Rabbi Yitzchak were walking from Beit Meron to Tzippori and met a young man carrying wine spiced with honey. Rabbi Yitzchak opened with the verse "and your palate is like the best wine, that goes down smoothly for my beloved," explaining that this refers to the wine of Torah, good for this world and good for the world to come. The young man sharply noted that the text says "like the best wine" and not "of the best wine," for which Rabbi Yehuda praised him.<br />