...אמרו עליו על הלל הזקן שבכל יום ויום היה עושה ומשתכר בטרפעיק חציו היה נותן לשומר בית המדרש וחציו לפרנסתו ולפרנסת אנשי ביתו פעם אחת לא מצא להשתכר ולא הניחו שומר בית המדרש להכנס עלה ונתלה וישב על פי ארובה כדי שישמע דברי אלהים חיים מפי שמעיה ואבטליון אמרו אותו היום ערב שבת היה ותקופת טבת היתה וירד עליו שלג מן השמים כשעלה עמוד השחר אמר לו שמעיה לאבטליון אבטליון אחי בכל יום הבית מאיר והיום אפל שמא יום המעונן הוא הציצו עיניהן וראו דמות אדם בארובה עלו ומצאו עליו רום שלש אמות שלג פרקוהו והרחיצוהו וסיכוהו והושיבוהו כנגד המדורה אמרו ראוי זה לחלל עליו את השבת...
...It is reported about Hillel the Elder that every day he used to work and earn one tropaic, half of which he would give to the watchman at the house of study; the other half he used on food for himself and the members of his household. One day he was unable to earn anything, so the watchman at the house of study did not let him in. He then climbed [to the roof] and hung on, sitting over the opening of the skylight, so that he could hear the words of the living God from the mouths of Shemaiah and Avtalion. It is said that the was a Sabbath eve in the winter solstice, and snow came down on him from heaven. When the dawn rose, Shemaiah said to Avtalion, "Brother Avtalion, every day this house is bright with light, but today it is dark. Is the day cloudy?" When they looked up, they saw the figure of a man in the skylight. They climbed to the roof and found Hillel, covered with three cubits of snow. They removed the snow from him, bathed and anointed him, and, as they seated him in front of an open fire, they said, "This man deserves to have the Sabbath profaned on his behalf."...
(trans. William G. Braude: The Book of Legends (Bialik & Ravnitzky), p. 204
Guard of the study hall: Throughout Jewish history attitudes have varied with regard to payment for Torah study, especially at the highest levels. Apparently, in early generations, the preference was to have students of means who were not financially dependent on the community and were thereby free of the pressure that could accompany such support. Therefore, a fee was charged to enter the study hall. These fees were abolished by Hillel when he assumed his position of Nasi. Still, for several additional generations, guards were instructed to restrict entry to the yeshiva to students. Elsewhere the Gemara quotes Rabban Gamliel as saying: Any student whose inside, his thoughts and feelings, are not like his outside, his conduct and character traits, will not enter the study hall, which greatly limited the number of students (Berakhot 28a). Following severe upheavals, including the temporary impeachment of Rabban Gamliel of Yavne from his position as Nasi, this restriction was rescinded and the doors opened to all. [Source: Koren Steinsaltz Talmud, Yoma, p. 168]