Reb Yochanan Sofer writes that he remembers when he began to attend to his grandfather Reb Shimon Sofer zt”l for several hours during the day, the remaining hours that he utilized for learning were tremendously productive. In only a short period of time, he was able to understand the depths of the Gemora and the Rishonim; something that would normally have taken him days on end. This matter astounded him until he found that which the Chasam Sofer wrote: One who gazes at his Rebbe will merit a pure understanding of Torah. This can be derived from the possuk in Yeshaya [30:20]: And your eyes shall see your teacher. This is the explanation of our Gemora: Rabbi Chiya bar Abba said in the name of Rabbi Yochanan: If a teacher prevents his student from serving him, it is as if he is withholding kindness from him. The greatest kindness that a teacher can grant to his student is the ability to grasp the intricacies and greatness of Torah.