The poskim are divided as to whether sleep is considered a break after which it is necessary to repeat the recital of Birkot HaTorah.
According to most Rishonim, among them the Rosh, a person’s regular sleep in his bed is considered an interruption regarding Birkot HaTorah. The whole time a person is awake, the Torah continuously escorts and guides him. However, when a person sleeps, he ceases to think and his consciousness fades. Therefore, sleep is deemed an interruption regarding the mitzvah to learn Torah. Based on this, it is necessary in principle to recite Birkot HaTorah even after a nap during the day. Nonetheless, it has been customary to consider daytime sleep, even if it lasts a long time, to be temporary sleep, which does not constitute an interruption; hence, Birkot HaTorah recited in the morning are also effective after a daytime nap. However, regular sleep at night is an interruption and one must recite Birkot HaTorah after it. Therefore, one who needs to arise in the middle of the night for guard duty, and intends to return to sleep afterwards, recites Birkot HaTorah twice, once when he wakes up for guard duty, and a second time when he wakes up in the morning. That is the practice of Ashkenazim and many Sephardim (Shulchan Aruch, Orach Chaim 47:11; Mishnah Berurah 29).
There are those who say that sleep is not considered to be an interruption concerning Birkot HaTorah and that the law of Birkot HaTorah is similar to the law of Birkot HaShachar, which are recited once a day. Therefore, one who wakes up in the middle of the night for guard duty recites Birkot HaTorah after the first waking and does not recite them after the second time he wakes up (Kaf HaChaim 47:29; concerning the laws of Birkot HaShachar see earlier in this book 9:5).
. The Beit Yosef 47:11 and 13 explains that according to the majority of poskim, any regular sleep is considered to be an interruption. Yet, he cites Rabbeinu Tam, Ram, and Talmidei Rabbeinu Yonah, who maintain that Birkot HaTorah last until the Shacharit prayer of the next day. Even if he slept a regular sleep, it is not an interruption. In practice, the Beit Yosef concludes that only regarding regular sleep during the day do we take into consideration the opinions which maintain that it is not an interruption. That is what is written in Shulchan Aruch 47:13. However, regular sleep at night is considered to be an interruption and it is necessary to recite the blessings after it. This is what the Pri Chadash 47:13 and many other Acharonim write, as well as the Mishnah Berurah 47:29, based on the absolute majority of the poskim. That is also what is written in Yabia Omer 8:5. Some Acharonim suggest compromises, such as reciting all Birkot HaTorah the first time and one berachah the second time (Shut Maharsham 3:337). However, according to the majority of poskim, one must recite all Birkot HaTorah after every regular sleep at night. What is the definition of regular sleep? The Rosh writes that sleep is considered regular when one goes to sleep on his bed. Bei’ur Halachah, section 4:16 writes that the middle opinion regarding sixty breaths taken while sleeping is approximately half an hour. See the note in Yabia Omer there.Moreover, the Mishnah Berurah 47:25 writes that one who recites Birkot HaTorah after a regular sleep during the day does not lose out, because that is the opinion of the absolute majority of the poskim. (Additionally, according to most poskim, the obligation to recite Birkot HaTorah is biblical, and sefeika d’oraita l’chumra, when there is doubt concerning a biblical commandment, we are stringent.) Even so, the accepted minhag is not to recite the berachot. The Kaf HaChaim 25 writes in the name of the Ben Ish Chai, Vayeshev 12, that in order to avoid uncertainty it is best to recite the berachot in his thoughts. He further advises that while saying Birkot HaTorah in the morning one should have kavanah explicitly that they continue to last after sleep, for perhaps such kavanah will be effective. The Mishnah Berurah 13 suggests having kavanah to fulfill the obligation of Birkot HaTorah in the recital of Ahavat Olam in Ma’ariv, and after the berachah to say a verse for the sake of learning, for we learned in halachah 2 that Ahavat Olam is considered to be like Birkot HaTorah.
The opinion of the Ben Ish Chai, Vayeshev 13, also cited by the Kaf HaChaim 47:29, is that, according to Kabbalah, the law of Birkot HaTorah is similar to the law of Birkot HaShachar, that they are not recited twice in a 24-hour period. Their opinion is based on Rabbeinu Tam. However, according to Rabbeinu Tam, Birkot HaTorah are recited in the morning adjacent to Shacharit, and according to the Ben Ish Chai, if one slept twice at night, he recites the blessings after the first sleep and not after the second (and he should have kavanah in Ahavat Olam to fulfill the obligation of Birkot HaTorah). According to this, there is a certain distinction between Birkot HaShachar and Birkot HaTorah. Birkot HaTorah has two intentions: one, as part of Birkot HaShachar whose time starts after chatzot, and the second, as berachot before learning Torah. Therefore, one who wakes up close to chatzot should wait and recite Birkot HaTorah with Birkot HaShachar after chatzot. Yet, if he wakes up long before chatzot, he may recite them before chatzot alone. There were devout people who were accustomed even in such a case to wait and recite the blessings after chatzot.