Communal Prayer - תפילה בציבור ​Why I need you.
1א

אמר רבי אמי אין תפלתו של אדם נשמעת אלא אם כן משים נפשו בכפו שנאמר (איכה ג, מא) נשא לבבנו אל כפים [איני והא] אוקים שמואל אמורא עליה ודרש (תהלים עח, לו) ויפתוהו בפיהם ובלשונם יכזבו לו ולבם לא נכון עמו ולא נאמנו בבריתו ואף על פי כן (תהלים עח, לח) והוא רחום יכפר עון וגו' לא קשיא כאן ביחיד כאן בציבור

Rabbi Ami said: A man's prayer is not heard unless he puts his soul in his hand, as it is said: "Let us lift up our heart with our hands" (Eikha 3:4). Is that so? But surely Shmuel appointed an interpreter for himself and he expounded: "But they flattered Him with their mouth, and with their tongue they lied to Him, and their heart was not steadfast with Him, and they were not faithful to His covenant" (Tehillim 78:36-37). But even so, "He is merciful, He forgives sins, etc." (ibid. v. 38). There is no difficulty, Here [it refers] to an individual. Here [it refers] to a community.

2ב

(א) תפלת הציבור נשמעת תמיד ואפילו היו בהן חוטאים אין הקב"ה מואס בתפלתן של רבים לפיכך צריך אדם לשתף עצמו עם הציבור ולא יתפלל ביחיד כל זמן שיכול להתפלל עם הציבור

ולעולם ישכים אדם ויעריב לבית הכנסת שאין תפלתו נשמעת בכל עת אלא בבית הכנסת

​ וכל מי שיש לו בית הכנסת בעירו ואינו מתפלל בו עם הציבור נקרא שכן רע.

The prayer of a community is always heard, and even if there are sinners [amongst them], Hashem does not reject the prayers of the many. Therefore, it is necessary for a person to join with a congregation and not to pray alone whenever he is able to pray with a community.

One should always spend the early morning and evening [hours] in the synagogue, for prayer will not be heard at all times except [when recited] in the synagogue.

Anyone who has a synagogue in his city and does not pray [together] with the congregation is called a bad neighbour.

3ג

(ו) תקון המקום: כיצד? יעמוד במקום נמוך ויחזיר פניו לכותל וצריך לפתוח חלונות או פתחים כנגד ירושלים כדי להתפלל כנגדן שנאמר וכוין פתיחן ליה בעיליתיה וגו' וקובע מקום לתפלתו תמיד ואין מתפלל בחורבה ולא אחורי בית הכנסת אא"כ החזיר פניו לבית הכנסת ואסור לישב בצד העומד בתפלה או לעבור לפניו עד שירחיק ממנו ארבע אמות.

Proper place: What is implied?

One should stand in a low place and turn his face towards the wall. Also, one should open windows or doors that face Jerusalem and pray opposite them, as [Daniel 6:11] states: "...and he had windows open in his room facing Jerusalem."

A person should establish a fixed place where he always prays. One should not pray in a destroyed building, nor [should one pray] behind a synagogue, unless he turns his face towards the synagogue.

It is forbidden to sit down next to someone in the midst of the Amidah or to pass in front of him, except at a distance of four cubits

4ד

אמר ר' יוחנן בשעה שהקב"ה בא בבית הכנסת ולא מצא בה עשרה מיד הוא כועס שנא' (ישעיהו נ, ב) מדוע באתי ואין איש קראתי ואין עונה. א"ר חלבו אמר רב הונא כל הקובע מקום לתפלתו אלהי אברהם בעזרו

Said Rabbi Yochanan: The time that Hashem comes to the synagogue and does not find a minyan immediately, he becomes angry. As it is said (Isaiah 50:2) Why, when I came, was there no one?" When I called, there was no one to take an answer..."
Rabbi Chelbo said in the name of Rav Huna: All who sets a fixed place for Prayer, the G-d of Avraham will help him.

5ה

Rav Kook:

R Chanina said – A person should not pray in a room without windows”

Prayer is indeed a spiritual labor unique in the soul of one praying. However, the necessary condition for it to successfully effect the one praying, is the full knowledge of the value of the outside world. Then the perfect pleasantness will really have influence upon the one praying. However, for the person who’s individual prayer causes him to separate himself from the outside world, he will not arrive at the end purpose of prayer – which is to invigorate man to be ready to work with integrity and honesty according to the spirit of G-d that inspires him. Therefore, a person should only pray in a house that has windows, because the option of being able to see the outside world will inspire him to fulfill his duty to the world that he lives in….

6ו

תניא אבא בנימין אומר אין תפלה של אדם נשמעת אלא בבית הכנסת שנאמר (מלכים א ח, כח) לשמוע אל הרנה ואל התפלה במקום רנה שם תהא תפילה.

It was taught in a Braita that Abba Binyamin said: One's prayer is only heard in a synagogue, as it is said (Kings I 8:28) "to listen to the song and the prayer", In a place of song, there prayer should be.

7ז

The Kuzari – Communal Prayer

The Khazar king: Why is this? If everyone read his prayers for himself, would not his soul be purer and his mind less abstracted?

The Rabbi: Common prayer has many advantages. In the first instance a community will never pray for a thing which is hurtful for the individual, while the latter sometimes prays for something [to the disadvantage of other individuals, or some of them may pray for something] that is to his disadvantage. One of the conditions of prayer, craving to be heard, is that its object be profitable to the world, and not hurtful in any way. Another is that an individual rarely accomplishes his prayer without slips and errors. It has been laid down, therefore, that the individual recite the prayers of a community, and if possible in a community of not less than ten persons, so that one makes up for the forgetfulness or error of the other. In this way [a complete prayer is gained, read with unalloyed devotion. Its blessing rests on everyone] each receiving his portion. For the Divine Influence is as the rain which waters an area (if deserving of it), and includes some smaller portion which does not deserve it, but shares the general abundance…

A person who prays but for himself is like one who retires alone into his house, refusing to assist his fellow-citizens in the repair of their walls. His expenditure is as great as his risk. He, however, who joins the majority spends little, yet remains in safety, because one replaces the defects of the other. The city is in the best possible condition, all its inhabitants enjoying its prosperity with but little expenditure, which all share alike.

In a similar manner, Plato styles that which is expended on behalf of the law, "the portion of the whole." If the individual, however, neglects this "portion of the whole" which is the basis of the welfare of the commonwealth of which he forms a part, in the belief that he does better in spending it on himself, he sins against the commonwealth, and more against himself. For the relation of the individual is as the relation of the single limb to the body. Should the arm, in case bleeding is required, refuse its blood, the whole body, the arm included, would suffer. It is, however, the duty of the individual to bear hardships, or even death, for the sake of the welfare of the commonwealth. He must particularly be careful to contribute his "portion of the whole," without fail. (III, 18-19)