Why Rabbi Judah ben Ilai's Face Shone with Torah

A certain gentile saw Rabbi Judah ben Rabbi Il'ai, whose face was radiant. He said: This man has one of three things in him—either he lends at interest, or he raises swine, or he is a drinker of wine. Rabbi Judah ben Rabbi Il'ai heard his voice and said to him: May the spirit of that man expire! For not one of these is in me. I do not lend at interest, as it is written, "unto thy brother thou shalt not lend upon usury" (Deuteronomy 23:20). And I do not raise swine, for it is forbidden for a son of Israel to raise swine, as we have learned there, "A person may not raise swine in any place." And I am no drinker of wine, for the four cups of Passover that I drink at Passover bind up my head from Passover until Shavuot. Rabbi Mani's head was bound up from Passover until the Festival [of Sukkot]. He said to him: Then on what account is your face radiant? He said to him: It is the Torah that makes my face radiant, as it is written, "a man's wisdom maketh his face to shine" (Ecclesiastes 8:1). Rabbi Abbahu went to Caesarea and came back from there with his face radiant. His disciples saw that his face was radiant. They went up and said to Rabbi Yochanan: This Rabbi Abbahu has found a treasure. He said to them: How so? They said to him: Because his face is radiant. He said to them: Perhaps he heard some new Torah teaching. He went up to him and said to him: What new Torah teaching did you hear? He said to him: I recited an ancient tosefta. And he applied to him: "a man's wisdom maketh his face to shine" (Ecclesiastes 8:1).