One of the most important points about prayer is to offer the obligatory ones in congregation.
Praying the obligatory ones in congregation is a strong tradition of the Prophet (pbuh), never omitting praying them in congregation except during the last days of his life when he was seriously ill.
The following event that points out the importance of praying in congregation is a striking one:
One of the companions of the Prophet (pbuh) called Abdallah ibn Mektum, a blind man, once asked the Prophet (pbuh) to be excused from attending the congregation for the obligatory prayers:
"O Messenger of Allah! You know my position; there are many palm trees on my way to the mosque! And I cannot find a guide every time!"
The Prophet (pbuh) answered:
" – Can you hear the call for prayer?"
" – Yes, I can!"
" – Then, you are supposed to attend the congregation, even by crawling..." (I. Canan, Kutub al-Sitte, VIII, 256).
The Prophet (pbuh) says:
"Those who attend the mosque at dark will find a shade on the Day of Judgment when no shade is to be found." (ibn Maja).
Other sayings of the Prophet (pbuh) are to be found in this regard:
"The prayer offered in congregation is twenty seven times superior to the one offered on one's own." (Bukhari, Adhan, 30).
.".. The prayer done by two persons is superior to the prayer done by one person; the prayer done by three persons is superior to the prayer done by two persons. The more their number the more lovely their prayer is to Allah." (Abu Dawud, Nasai, Imamat, 45).
"Those who offer late-night prayer in congregation are regarded to have spent the first half of the night; and those who offer morning prayer in congregation are regarded to have spent the second half of the night praying." (Muslim, Masjid, 260).
"Those who attend congregation for five daily prayers regularly will pass the bridge from this world to Paradise like a thunder. Moreover, Allah will resurrect and assemble them for judgement among the second generation of Muslims after the Prophet. Those who attend congregation night and day will get as much reward as a thousand martyrs." (Camu'l-Fawaid, 246).
"Stand in proper lines while praying in congregation, because it is a sign of perfect prayer." (Abu Dawud, Salat, 93).
Praying in congregation advances the power of one's faith. It is a mirror of the Muslim community. The community of faith is kept through attending congregational prayer.
The Prophet (pbuh) says:
"The person who goes to mosque for prayer after making ablution at home is like the person who goes to the Ka'bah for pilgrimage after putting on ihram, a special cloth for pilgrimage." (Fadail al-Amal, 275).
This person is given a reward for every step he takes on the way to the mosque, and one of his/her sins is forgiven.
"S/he who prays in congregation from start to finish for forty days is given two titles of privilege. The first is salvation from hell. The second is distancing himself/herself from hypocrisy." (Muslim, Tirmizi).
Allah will ask on the Day of Judgment:
"Where are my neighbors?"
The angels will answer:
"O the Lord! Who are your neighbors?"
Allah will say:
"Those who regularly attend mosques."
The Prophet (pbuh) says:
"The mosque is the home of every sincere believer. And Allah assured these servants of all kinds of easiness, mercy, and convenience on the bridge from this world to Paradise." (Tabarani).
Attending congregation is so important that the Prophet (pbuh) seriously warned about the negative consequences of being careless about it. One of the sayings of the Prophet (pbuh) in this regard is as follows:
"The prayers of those who do not attend congregation though they hear the call for prayer and offer their prayer where they are with no reasonable excuse are not accepted."
The companions asked him:
"O Messenger! What is to be regarded as an excuse?"
The Prophet (pbuh) said:
"It is illness or fear of danger." (Abu Dawud, ibn Maja).
If a group of people cannot join congregation at mosque, they are supposed to offer their prayer together where they are. The Prophet (pbuh) said in this regard:
"If a group of people of three in a village or countryside do not perform their prayer together, Satan will impose himself on them. Try to offer your prayer with other people, and do your best to join congregation; because the wolf eats a lonely sheep." (Abu Dawud, Ahmad, Nasai).
Attending congregational prayers for the morning and late-evening prayers is of great importance. The Prophet (pbuh) says:
"He who offers late-evening prayer in congregation is regarded to have worshipped in the first half of the night; and he who offers morning prayer in congregation is regarded to have worshipped in all parts of the night." (Muslim).
"If people knew the virtue of the call for prayer and standing in the first line of congregation, and if they had no other chance, but drawing lots in order that they could be the one to call for prayer and stand in the first line, they would go for drawing lots. If they knew the virtue of being an early comer for prayer in congregation, they would contest among themselves. And if they knew the reward for morning and late-evening prayer, they would attend them even by crawling." (Bukhari, Muslim).
So, a believer is supposed to lend his heart to prayer, and his ears to the call for prayer. Participation in congregation begins with participation in the call for prayer. The companions of the Prophet (pbuh) used to stop all their worldly engagements while the call for prayer was being recited in order to get ready for the mood of prayer. The hands that swung hammers and the tongues that speak used to stop, and the roads were only for the mosque. Their hearts filled with the love of Allah used to follow the guidance described by the Prophet (pbuh):
"When you hear the call for prayer, repeat the words said by the caller! Then pronounce the formula calling Allah's benediction on me! Whoever pronounce the formula calling Allah's benediction on me, Allah grants him ten benefactions in return. This is so great a rank in paradise that it is given only to one servant. And I myself wish to be that person. And whoever wishes my intercession, it is granted to him." (Muslim, Salat, 11).
He who goes to the mosque without enjoying the deep and spiritual meaning of prayer as described above gets no blessing out of his action. The saying of the Prophet (pbuh) is to be remembered in this regard:
"The person gets what he intends by coming to the mosque." (Abu Dawud).
On the other hand, attending congregation accustoms the person with a facility to keep his life under control, and acts as an agent to regiment the person's disorganized life.
The saying of the Prophet (pbuh), "Does not the person who raises his head from the position of prostration before the leader of the prayer fear that Allah might turn his head into that of donkey?" (Bukhari, Muslim), points out that disorganized individuals can be trained through prayer and the individual thus can be prepared to duly stand in the presence of Allah. Otherwise, order and stability cannot be established in prayer.
The final word about prayer in congregation is that every believer should have his heart attached to the mosque; because among seven groups of people who are promised Divine shade by Allah on the Day of Judgment when there is no other shade that will exist is the group of believers "who have hearts clinging to the mosque."