Rabbi Shimon says, “One who walks on the road while reviewing [a Torah lesson] but interrupts his review, and exclaims, ‘How beautiful is this tree! How beautiful is this plowed field!” – Scripture considers it as if he is liable to pay with his life (Avot 3:7).
Rabbi Elazar b’Rabbi Tzadok rules that one should not say, “Gezuntheit,” “Labriut,” or, “G-d bless you” when someone sneezes in the Beit Hamidrash, in order not to waste time from Torah study (Tosefta, Shabbat 7).
He would say, “Why do talmidei chachamim perish in their youth? They are not immoral and they do not steal, but it is due to bitul Torah” (Avot d’Rabbi Natan, I, 26:2).
Yerushalayim was destroyed only on account of bitul Torah (Avot d’Rabbi Natan, II, 5)
One who has not sinned with bitul Torah yet nonetheless suffers, should know that his suffering is that of love, as the pasuk states (Tehillim 94:12), “Praiseworthy is the man whom G-d disciplines, and who You teach from Your Torah” (Berachot 5b).
Rains are withheld due to bitul Torah, as the pasuk (Kohelet 10:18) states, “Through laziness the ceiling sags.” When Bnei Yisrael were remiss in Torah study, the skies were sealed (Ta’anit 7:2).
Our Sages say that one who frequents the bullfights and circuses often sees fortune-tellers and people practicing various forms of witchcraft. Assorted types of amusement include jesters and mimes. These categories of entertainment are considered the “seat of scoffers.” Regarding them, the pasuk states (Tehillim 1:1-2), “Praiseworthy is the man who has not walked in the counsel of the wicked… and has not sat in the company of scoffers. But his desire is in the Torah of Hashem.” From here we see that these forms of pastimes remove a person from Torah study (Avodah Zarah 18b, see Rashi).
Hashem overlooked the sins of idolatry, immorality, and bloodshed, but He refused to overlook the sin of bitul Torah (Yerushalmi, Chagigah 1:7).
Rabbi Yehudah Hanasi says that one’s children die in childhood on account of bitul Torah, as the pasuk says, “In vain did I strike your children, for they did not accept rebuke” (Yalkut Shimoni, Yirmeyahu, remez 266).
Just as the reward for Torah study surpasses that of all other mitzvot, so does the punishment for bitul Torah surpass those of all other aveirot (Sifri, Eikev).
In punishment for bitul Torah, Amalek attacked Am Yisrael. Tragedies come upon the world as punishment for neglecting Torah study (Rabbeinu Bachya, Shemot 13).
Learning Torah for one hour and then stopping for an hour is an exercise in futility. It is like someone who plants and then washes away his seeds. The main aspect of Torah study is its consistency. Therein lies the secret of its sanctity. One who learns in a fragmented way will be left with nothing. A person should plan out how he will acquire diligence in Torah study and constantly pray for his success (Igrot HaChazon Ish).
