Rabbi Tzvi Felman zt"l recounted that one summer day when he was studying at the Ponevezh Yeshiva there was a particularly hot day, and it was difficult to sit down to study. There was a slight feeling of lethargy from the heavy heat, there were no air conditioners in the sitting, there were hardly any fans, and as a result it was very hot. In the afternoon, when the fever increased, the Rabbi said to his chavruta: "Let's go down to the Chazon and see what he is doing today, if he sits and studies as he always does, it is a sign that the heat is not a reason to stop studying, and we must continue to learn."
In fact, the two young men went down to the Chazon Ish's house to see and learn from him a great deal. They entered the room of the Gaon Yisrael in awe. And they saw the Chazon Ish sitting at the table with the Gemara and the books, completely immersed in the toil of the Torah as he usually did every day. In the Chazon Ish's room it was as hot as in all other places. There were also many flies and other flying birds in the room, since Bnei Brak was built near the orchards. And from there they came flying into the houses. All of this did not affect the Torah labor of the Chazon Zohar, and they did not see any difference between this day and the other days. The sight of the Chazon on such a day, and in such a situation, provided them with an immediate answer to the question for which they came: There is no difference between this day and the other days, and the mitzva of the Torah is performed on the same level as on other days. However, the great wonder is that how can one learn without being disturbed by the great heat and the many flies that came as a result of the heat, the young man decided that he must ask this question to the Chazon Tzvi himself. He approached the Chazon Zohar. In order to wait for a moment, he lifted his eyes from the Gemara and noticed him, but for a moment he delayed. But the young man did not give up, and decided to wait until he received the answer to his question.
After about half an hour, the Chazon Zohar noticed him and asked him what he wanted. The young man began to ask, "How can you learn when the whole room is full of so many flies?" The Chazon Zohar answered by arranging his glasses to see and look for the flies that fill the room, and as he did so, he answered, "I don't see anything." If the Chazon Zohar does not see the flies, and therefore they do not bother him, then what can be asked? So the young man turns to the second and main question, after all, the heat is felt even without seeing it, and he says to the Chazon Zohar that it is very hot today, "How can you study with such heat?" The Chazon Zohar is very surprised and says, "Is it hot today? And it seemed that the Chazo wondered what that young man wanted, he sat and studied and did not feel either the flies or the heat. The Chazon Zohar, who saw the young man amazed at this answer, continued, "You should know, the flies and the heat are only until you enter the sugya, but from the moment you enter the sugya, there are no flies and no heat, you don't feel anything!"
