Biblically, the time of the Keriat Shema of Ma’ariv lasts the whole night, for it is written, “beshochbecha,” “when you lie down,” and people normally lie on their beds throughout the entire night. However, the Chachamim “created a fence” to this law and established its time until chatzot (halachic midnight), so that a person won’t postpone the recital of Keriat Shema, then fall asleep and miss it. Nevertheless, b’dieved, if the time passed, and he did not recite it before chatzot, he says it with its berachot before amud hashachar (dawn), since biblically, the time to recite it lasts the whole night.
A person who found himself in circumstances beyond his control and did not recite Shema before amud hashachar has until netz hachamah (sunrise) to do so (these times are clarified earlier in this book 11:2). When reciting Shema after amud hashachar, it is said with three berachot, though without Birkat Hashkiveinu, for since amud hashachar already arrived, it is no longer considered time “to lie down.” Ma’ariv may not be prayed after amud hashachar either, because it was instituted for the night, and after the break of dawn, daytime has already begun (Mishnah Berurah 235:34; Sha’ar HaTzion 41).
L’chatchilah, it is preferable to recite Shema and pray Ma’ariv immediately after tzeit hakochavim, for those who are expeditious perform mitzvot early. However, someone who is engrossed in Torah study is permitted l’chatchilah to delay his prayer until after his learning, as is done in many yeshivot where it is customary to pray Ma’ariv at the end of the afternoon learning session and not immediately at tzeit hakochavim. Similarly, a person who prefers to pray in a late minyan because he believes he will be able to concentrate better is permitted l’chatchilah to delay his prayer. Obviously it is better to pray in a late minyan rather than to pray individually immediately after tzeit hakochavim.
. The Mishnah in Berachot 2a states that, according to the Chachamim, the time of Keriat Shema lasts until chatzot, and according to Rabban Gamliel, it is until amud hashachar. In the Gemara 8b, the conclusion is that the halachah follows Rabban Gamliel. That is also how the Rosh and Rashba rule, that it is permissible l’chatchilah to recite Shema until amud hashachar. However, the opinion of the Rif, Rambam, Smag, and the majority of Rishonim is that its time is until chatzot, and only if the time passed and one did not recite it until then, he may recite it until amud hashachar. In such a case the Gemara teaches that the halachah follows Rabban Gamliel (and perhaps that is the opinion of Rabban Gamliel himself). That is how the Shulchan Aruch 235:3 rules. The Bei’ur Halachah supports this opinion. (Regarding the Chachamim’s opinion, the Rishonim disagree: according to Talmidei Rabbeinu Yonah, the Chachamim maintain that one cannot recite Keriat Shema after chatzot, and according to the Smag, b’dieved, it can be recited after chatzot. The Gra explains that the Bavli and the Yerushalmi are divided concerning this. According to the Bavli, the Chachamim maintain that b’dieved one may recite Shema after chatzot, and according to the Yerushalmi, one may not. Additionally, see Beirur Halachah Berachot 2a.)
The time of the Amidah of Ma’ariv: according to the Derech HaChaim, l’chatchilah, lasts until chatzot, and according to the Pri Megadim, lechatchilah, it is all night. These opinions are cited by the Mishnah Berurah 108:15. (See earlier in this book, chapter 17, note 13, concerning the matter of someone who is traveling and finishes his trip after chatzot.) Or L’Tzion, part 2, 15:9, writes that it is preferable to pray individually before chatzot rather than in a minyan after chatzot.
. If, because of circumstances beyond his control, one recites the Ma’ariv Shema after amud hashachar, he cannot fulfill his obligation of the daytime Shema before netz that same day, for after treating this time as a time to lie down, he cannot consider it also a time to get up (Shulchan Aruch 58:5; Mishnah Berurah 22). However, there are those who say that after the time of misheyakir he may recite the Shema of Shacharit (Kaf HaChaim 58:21).
The Mishnah Berurah 235:30 explains that, biblically, it is permissible to recite the Keriat Shema of Ma’ariv until netz; since at that time there are still people lying in their beds, it is called a time of “when you lie down.” However, at amud hashachar, the day already begins, and therefore the Chachamim established not to recite the Shema of Ma’ariv after amud hashachar. Only someone who did not recite the Shema before amud hashachar due to circumstances beyond his control is permitted to recite it until netz. Rav Kook in Tov Ro’i 55 clarifies that, biblically, the time for the nighttime Keriat Shema is until amud hashachar and the Chachamim instituted that one who finds himself in circumstances beyond his control can make it up until netz.