Since the Chachamim instituted the recital of Shema together with its berachot, and established praying the Amidah immediately following, l’chatchilah the time of Shacharit should be set to allow people to succeed in reciting Shema before the first three hours of the day have ended according to the Magen Avraham.
When the congregation is late to pray and there is concern that those praying will recite the Shema after the time according to the Magen Avraham, the people praying should be instructed to recite the paragraph of Shema before beginning to pray. One who wishes to enhance the mitzvah should read all three paragraphs.
When the congregation prays even later and recites the Amidah after the time to pray has already ended according to the Magen Avraham, the poskim disagree as to what is preferable. There are those who say that it is better to pray in a minyan within four hours according to the Gra, because that is the opinion of the majority of poskim. Further, the time of Shacharit is rabbinic and we are lenient when there is uncertainty regarding rabbinic rulings. Additionally, in cases of extenuating circumstances one may recite Shacharit until chatzot. Therefore, it is best to pray in a minyan as the Chachamim established, even if the congregation prays after the time to pray has ended according to the Magen Avraham. Nevertheless, there are those who say that it is better to pray individually at the proper time according to the Magen Avraham, rather than to pray in a minyan after the time to pray has ended according to him.
However, if the minyan is not conducted in accordance with the halachah and prays after four hours have passed according to the Gra, all opinions agree that one must pray individually prior such a late minyan.
One who does not have tefillin must not delay praying until after the time of Keriat Shema and the Amidah, when he will have them, since b’dieved one is permitted to fulfill the mitzvah of Keriat Shema and the Amidah without tefillin (Mishnah Berurah 46:33; further in this book 12:9).
.According to the majority of poskim, only the recital of the first verse is a biblical obligation and therefore the Beit Yosef and the Rama section 46:9 write that it is good to say the first verse of Shema in the Korbanot passages so as to fulfill one’s obligation of Keriat Shema with its recital. The Mishnah Berurah 46:31 writes that some say the whole first paragraph must be recited, while others say the first two paragraphs (because according to the Pri Chadash both are biblical obligations). Ideally a person should recite all three paragraphs, because according to the Pri Chadash it is good to fulfill one’s obligation of remembering the Exodus during the time that one recites Keriat Shema.
However, according to the Gra, based on the Ra’ah, it is not proper to fulfill one’s obligation of reciting Keriat Shema without its blessings. Nevertheless, in this case, in order to fulfill the obligation of reciting it within Magen Avraham’s time frame, it is better to recite it earlier by itself (Bei’ur Halachah 46:9, s.v. “V’Yotzeh”). Whoever sees that the congregation is going to miss the time of Keriat Shema according to the Magen Avraham by a few minutes, Shut Binyan Olam, Orach Chaim 4, writes that he may say it earlier with its berachot and wait at “Shirah Chadashah” for the congregation, thereby meriting the recital of Keriat Shema with its berachot within the time of the Magen Avraham, as well as prayer in a minyan.
Rabbi Akiva Eiger writes that a person who is uncertain as to whether he will succeed in reciting Keriat Shema with its berachot according to the time of the Magen Avraham must recite it before then with a stipulation that if the halachah is like the Gra’s approach or if the congregation ends up reciting Keriat Shema on time, he does not intend to fulfill his obligation with that recital, and will instead fulfill his obligation with the Shema that he will recite together with its berachot. However, Da’at Torah and Oneg Yom Tov 3 write that a stipulation cannot be effective for a biblical commandment. Indeed, the Acharonim are in disagreement regarding this. Most poskim mention in practice the advice given by Rabbi Akiva Eiger, as written in Yalkut Yosef 58:5 and Ishei Yisrael 18:18.
. Minchat Yitzchak 3:71 writes that it is preferable to pray in a minyan at the time specified by the Gra. So writes the Avnei Yashfeh 8:12. By contrast, it is the opinion of Rabbi Shlomo Zalman Auerbach (brought by Ishei Yisrael 18, note 40) that it is preferable to pray individually at the time specified by the Magen Avraham. Likewise, regarding the Sephardic minhag, there is disagreement. Minchat Yitzchak writes there that according to Sephardim as well it is preferable to pray in a minyan, However, Rav Abba Shaul writes that Sephardim practice according to the Magen Avraham and it is preferable that they pray individually instead of in a minyan after the time of the Magen Avraham. The Yalkut Yosef 89:6 writes that whoever always practices according to the Magen Avraham and knows that he will have kavanah throughout the entire Amidah, it is preferable that he prays individually within the time of the Magen Avraham. However, if he cannot concentrate well, it is best that he prays with the congregation, for then his prayer is heard.Chazarat HaShatz must be concluded within the first four hours of the day (Mishnah Berurah 124:7). The Or L’Tzion, part 2, 7:25 writes in a footnote that one may not start Chazarat HaShatz after four hours have passed. Bei’ur Halachah 124:2 s.v. “Sheya’avor” is uncertain regarding this, for perhaps since the time of prayer lasts b’dieved until chatzot, it is possible to recite Chazarat HaShatz even after the conclusion of four hours.
. When a person prays earlier than the congregation because the minyan is late, some say he should pray outside the synagogue, and others say that because they are not practicing in accordance with halachah, he is permitted to pray earlier in their presence. See Mishnah Berurah 90:35. It seems that if by his praying earlier in front of the congregation, the people will learn from him and pray earlier too, it is best that he prays in front of them, However, if they will not learn from his example, it is preferable that he prays individually elsewhere.