How can Chachomim nullify my recitation of the evening Shema if I read it at a time permitted by the Torah?

Question

The Mishnah Berurah (OC 235:30) writes:

לא יצא וכו' - דאף דמן התורה קרינן בשכבך עד הנץ משום דאיכא עדיין מקצת אנשים דגנו בההיא שעתא מ"מ היכא דלא איתנס בטלו חכמים ממנו מצות ק"ש על שאיחר כ"כ ואינו יוצא ידי חובתה שוב בקריאתה

Even though we say that from the Torah which says “when you lie down”, you can fulfill the mitzva of reading the Shema up to sunrise, that's because of the few people who go to bed at that time. However, where it's not an unavoidable case, the Chachomim nullified his recitation of the Shema because he delayed so long and he will not have fulfilled his obligation by reading it then.

How can Chachomim do that ? Are there other cases like it?

Answer 1

I believe the R Yona in the beginning of Brachos asks your question,

ויש להקשות לרבנן דאמרי דאפי' דיעבד אינו יוצא אלא עד חצות, אם עבר חצות מה יהא דינו. שאם נאמר שלא יקרא כלל קשה, כיון דק"ש חיוב מן התורה היאך יכולין חכמים לפטרו ממנה. ואית דאמרי, דסבירא להו דאחר חצות קורא אותה בלא ברכות שהברכות אינן אלא מדרבנן, יכולים הם בשלהם למנוע שלא יאמר אותן אחר שעבר זה הזמן. אבל ק"ש שהוא מן התורה קורא אותה כל הלילה וכו'. ונראה למורי הרב נר"ר דסבירא להו לרבנן שאפי' ק"ש עצמה שהיא מן התורה כל הלילה אינו קורא אותה אחר חצות, שיכולים חכמים לפטרו ממצות עשה כל זמן שעושין כן משום סייג או משום קיום המצוה עצמה, דהכי חזינן 'בלולב וכו'. וגבי סדין בציצית נמי וכו

It seems like the אית דאמרי agree with your question, that's why they propose that the Chazal didn't really nullify the biblical Mitzvah of Krias shema, only the blessing (ברכות) that accompanies it. But the R Yonah himself holds that the Rabbis can do such a thing when they deem it necessary for the Mitzva (קיום המצוה עצמה), as he goes on and brings support to his answer from other places in the Talmud.

Regarding your second question, see also (besides for the R Yonah that also addresses this question) first Mishna in Brachos, where it compares it to all sacrifices (כל הנאכלים ליום אחד). There too it is biblically permitted to eat them the entire night, but the sages said only until midnight "להרחיק את האדם מן העבירה".

Answer 2

The עדות ביהוסף, the מרכבת המשנה and the זיו משנה on the Rambam (Krias Shema 1:10) give the simple answer, that the Gemara (Brachos 9a) says that you can say Krias Shema until Neitz relying on the opinion of Rabbi Shimon Bar Yochai in time of need. But that only applies in a time of need, otherwise the halacha is like the Chachamim that it is simply not the time of Krias Shema. Note that they are explicitly arguing with the Kesef Mishna's understanding of the Chachamim's position.

It seems pretty clear that the Mishna Brura isn't understanding it their way.

The Kesef Mishna to the Rambam (ibid) says:

ונ"ל טעמן של דברים שהתורה אמרה בשכבך בשעה שדרך בני אדם שוכבין מסרה הדבר לחכמים שיפרשו עד אימתי הוי זמן שכיבה והם פירשו דעיקר זמן שכיבה הוי עד שיעלה עמוד השחר ולפיכך זמן קריאה בזמן הזה שוה לכל אדם אפילו למזידין ולפי שאחר שעלה עמוד השחר קודם שתנץ החמה איכא אינשי דגנו בההיא שעתא אמרו דאכתי הוי זמן שכיבה לגבי אנוסין אבל למזידין אמרו דכיון דרוב בני אדם קמו באותה שעה לא מיקרי תו זמן שכיבה

The reason for this is that the Torah says "when you lie down" - at the time that people lie down to sleep and [the Torah] gives it over to the sages to say until when the time of sleeping [ends], and [the sages] explain that the main time of sleeping is until dawn even for those who deliberately delay until then, but after dawn before sunrise there are people who fall asleep then so they said it is still a time of lying down for those who were forced, but for those who deliberately delayed they said since most people are waking up then it is no longer called the time of lying down.

The Divrei Yirmiyahu on the Rambam (ibid) says that this is a case where if you don't follow what the Chachamim say, even Min HaTorah you have not fulfilled your obligation. For evidence of this, he quotes Tosfos to Sukka 3a דאמר who says that one who eats in a small Sukka with the table outside the sukka in the house - which is forbidden as a decree lest he lean out of the sukka on to the table to eat - even Min HaTorah he has not sat in the Sukka.

The עמק הלכה from Rabbi Moshe Aharon Alufin, Number 5:6 says (after a long discussion justifying the view that Rabbeinu Yona holds that you are not allowed to say Shema after the time the Chachamim forbid it, like you are not allowed to blow Shofar on Shabbos Rosh Hashana - which seems to be the opinion of the Gra to SA OC 235) that the Chachamim set the time until Chatzos and you can't fulfill the obligation afterwards. The context there is according to the opinions that you can't say it after midnight, but the idea would seem to be equally applicable to not saying it after dawn.

For evidence of this he cites Tosfos to Bava Basra 48b תינח where he says that the Chachamim can uproot something from the Torah means they can make an action ineffective (i.e. Kiddushin) even when it was done explicitly without any stipulation of relying on the Chachamim, and against their wishes.

Any one of those last three views could be made to fit in the Mishna Brura (especially the first and the third).

Answer 3

They nullified the eligibility of saying it during that the window of time (midnight to dawn), not the mitzvah if said. "בטלו חכמים ממנו מצות ק"ש" means "the Sages nullified from him the duty of saying Shema" after first light; and not (as you assume) their nullifying the reward of the mitzvah once done. In other words, the idea is that if first light came around without saying Shema yet, they tell you not to say it and feel the loss. This way, people will be more careful to say Shema while still fully night, and Shema would end up being said more often overall.

In line with other gezeiros (rabbinic legislation passed to prevent accidental violation of Torah law) that allow non-performance of a Torah duty for the sake of preventing a greater problem. Like not blowing Shofar on Rosh haShanah on Shabbos, as people were carrying shoferos around in a public domain to find someone to blow it / to show them how to blow it.