Hillel used to earn a trepik a a day, half of which he gave to the guard at the house of study and half he used to support himself and his family. One day he earned nothing and the guard would not let him in. He climbed up and sat on the skylight so that he could hear the words of the living God from Shemayah and Avtalyon. It happened that it was a Friday in the winter and the snow from the sky fell upon him. At the break of dawn, Shemaya said to Avtalyon, "My brother. Usually it is light but today it is dark. Perhaps the day is cloudy." They looked up and saw the shape of a man against the window, and they found three cubits of snow upon him. They took off the snow, washed him, anointed him and put him by the fire. They said "He is worthy for shabbat to be profaned for his sake." (Yoma 35b)

Why did they charge money for entry into the beit medrash? Maharsha raises two possibilities. The study halls in talmudic times were often out in the country and not in the heart of civilization. Out in the wild, one needs a guard and someone has to fund the salary of that guard. Alternatively, some study halls only let certain quality student in (see Berakhot 28a) and someone needed to pay for the guards who would administer this policy. These explanations of Maharsha raise a significant point. Yeshivot, shuls and other Jewish institutions do have financial needs and to some degree, they need to function like a business. At the same time, if they functions only like a business, things have gone very wrong. When a student of the dedication of Hillel is locked out because of one time that he could not pay, the business side of the yeshiva has become too dominant. Professor Yonah Frankel points out that Shemaya's comment about Hillel blocking the skylight may have symbolic import. The study hall is normally a great source of spiritual illumination. When small mindedness forces a Hillel to endanger himself in order to hear a shiur, it is indeed a dark day in the beit medrash.