All praise be to Allah and peace be upon the Messenger of Allah. I bear witness that there is no god but Allah alone who has no partner and I bear witness that Muhammad is His Servant and Messenger.
Many texts from the Qur'an and the Sunnah spoke about the virtues of masjids, their building, and taking care of them. Allah (may He be Exalted) says: "The Mosques of Allâh shall be maintained only by those who believe in Allâh and the Last Day, perform As-Salât (Iqâmat-as-Salât), and give Zakât and fear none but Allâh. It is they who are on true guidance." [Surat At-Tawbah: 18].
Al Bukhari and Muslim reported in their books of authentic Hadiths from the Hadith of `Uthman ibn `Affan (may Allah be pleased with him) that the Prophet (peace be upon him) said: "Whoever establishes a masjid for the sake of Allah, Allah will build for him a similar one."
Al Bazzar reported in his Musnad from the Hadith of Anas that the Prophet (peace be upon him) said: "There are seven items for which a person is rewarded while he is in his grave after death: Whoever teaches knowledge, digs a stream or a tunnel, digs a well, plants a palm tree, builds a mosque, gives a copy of the Qur'an in inheritance, or leaves an offspring to seek forgiveness for him after his death."
Masjids must be cleaned, perfumed, cleaned from dirt and bad odors.
Imam Ahmad reported in his Musnad from the Hadith of `A'ishah (may Allah be pleased with her) who narrated: "The Messenger of Allah (peace be upon him) commanded us with building masjids in homes, and commanded that they should be cleaned and perfumed."
It was reported in Sahih Al Bukhari and Sahih Muslim from the Hadith of Abu Hurayrah (may Allah be pleased with him) that a black woman used to clean the masjid [of the Prophet].The Messenger of Allah (may peace be upon him) missed her (or him) and inquired about her (or him). The people told him that she (or he) had died. He asked why they did not inform him, and it appears as if they had treated her (or him) or her (or his) affairs as of little account. He (the Holy Prophet) said: Lead me to her (or his) grave. They led him to that place and he said prayer over her (or him) and then remarked: Verily, these graves are full of darkness for their dwellers. Verily, the Mighty and Glorious Allah illuminates them for their occupants by reason of my prayer over them. In another narration: "She used to pick up torn pieces of cloth and sticks from the masjid." 
It was reported in Sahih Al Bukhari and Sahih Muslim from the Hadith of Jabir ibn `Abdullah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "He who has eaten onion, garlic, or leek should not approach our mosque, because the angels are also offended by the strong smells that offend the children of Adam."
Things of bad odor take the same ruling of those foods, on the top is the prohibition of smoking or what is so-called narghile. Prohibition was given also to searching for straying animal and contracting transactions in masjids. Imam Muslim reported in his Sahih on the authority of Abu Hurayrah that the Prophet (peace be upon him) said: "If anyone hears a man inquiring in the mosque about something he has lost, he should say: May Allah not restore it to you, because masjids were not built for that."
At-Tirmidhy reported in his Sunan from the Hadith of Abu Hurayrah that the Prophet (peace be upon him) said: "When you see someone buying or selling in the mosque, say to him: Say to him: `La Arbaha-Allahu Tijarataka (May Allah not make your bargain profitable)!" 
The same ruling goes for begging inside masjids, and drawing their attentions away from the glorification, Takbir (saying: "Allahu Akbar [Allah is the Greatest]"), Tahlil (saying: La Ilaha Illa Allah [No god but Allah]), and Dhikr in general under pretext of poverty and need.
Scholars have differed regarding the ruling of begging in masjids. The Maliki school of Fiqh and those who hold the same view adopted the prohibition of begging and held the previous Hadith as a proof to the prohibition of searching for lost items inside masjids. The same ruling goes for transactions, purchasing, lease and suchlike, and the reprehensibility of raising the voice in masjids for teaching and suchlike.
Al Shafi`ay school of Fiqh adopted the view of reprehensibility and held the Hadith of `Abdullah ibn Abu Bakr As-Siddiq as a proof in which he said: The Messenger of Allah (peace be upon him) said: "Is there anyone of you who provided food to a poor man today? Abu Bakr said: I entered the mosque where a beggar was begging; I found a piece of bread in the hand of `Abdal-Rahman which I took and gave it to him." 
Shaykh-ul-Islam Ibn Taymiyah (may Allah bestow mercy on his soul) was asked about this issue and he answered as follows: The origin of begging is forbidden whether inside or outside masjids except for a necessity. So, if a person is in need and he begged people in masjid without harming anyone by passing people and without telling lies when stating his conditions without speaking aloud to harm people such as asking while the Imam is preaching or while people are listening to a lecture and suchlike, it will be permissible, and Allah knows best. 
There are many Hadiths reported about the prohibition of decorating masjids and over exaggeration in spending money for that. Imam Ahmad reported in his Musnad narrated from the Hadith of Anas (may Allah be pleased with him) that the Prophet (peace be upon him) said: "The Last Hour will not come until people vie with one another about mosques."
Abu Dawud reported in his Sunan from the Hadith of Ibn `Abbas (may Allah be pleased with him) who narrated that the Messenger of Allah (peace be upon him) said: "I was not commanded to build high mosques.  Ibn Abbas said: You will certainly adorn them as the Jews and Christians did."
Sa`id ibn Mansur reported in his Sunan from the Hadith of Abu Hurayrah (may Allah be pleased with him) who narrated that the Messenger of Allah (peace be upon him) said: "When you decorate your masjids, and adorn your copies of the Qur'an, destruction shall inflict you." 
The Prophet's masjid was so humble and did not have any decorations or adornments. Al Bukhari reported in his Sahih from the Hadith of Nafi` ibn `Abdullah ibn `Umar (may Allah be pleased with him) told him that in the lifetime of Allah's Messenger (peace be upon him) the mosque was built of adobes, its roof of the leaves of date-palms and its pillars of the stems of date-palms. Abu Bakr did not alter it. 
It was reported in Sahih Al Bukhari that `Umar commanded with the building of the masjid saying: To protect  people from rain, and beware not to add reddish or yellowish substances to tempt the people.  Anas said: People shall boast of masjids then they shall not go to them but rarely. 
Caring for masjids is not limited only to building them but offering Salah therein and mentioning Allah, invoking Him, seeking forgiveness, and attending sessions of knowledge therein. Allah (may He be Exalted) says: "In houses (mosques), which Allah has ordered to be raised (to be cleaned, and to be honored), in them His Name is glorified in the mornings and in the afternoons or the evenings, * Men whom neither trade nor sale diverts them from the Remembrance of Allah (with heart and tongue), nor from performing As-Salat (Iqamat-as-Salat), nor from giving the Zakat. They fear a Day when hearts and eyes will be overturned (from the horror of the torment of the Day of Resurrection)." [Surat An-Nur: 37]. [Surat An-Nur: 36 - 37].
Imam Muslim reported in his Sahih from the Hadith of `Uqbah ibn `Amir who said: "When we were in Suffah, the Messenger of Allah (may peace and blessings be upon him) came out and said: Which of you would like to go out every morning to Buthan or Al `Aqiq and bring two large she-camels  without being guilty of sin or without severing the ties of kinship? We said: O Messenger of Allah, we would like to do it. Upon this he said: Does not one of you go out in the morning to the masjid and teach or recite two Ayahs from the Book of Allah, the Majestic and Glorious? That is better for him than two she-camels, and three Ayahs are better (than three she-camels) and four Ayahs are better for him than four (she-camels), and to on their number in camels." 
Imam Muslim reported in his Sahih from the Hadith of Abu Hurayrah who narrated that the Prophet (peace be upon him) said: "Any group of people that assemble in one of the Houses of Allah to study the Qur'an, tranquility will descend upon them, mercy will engulf them, angels will surround them and Allah will make mention of them to those (the angels) in His proximity." 
The status of masjid in Islam is great, therefore when the Prophet (peace be upon him) arrived at Medina, the first action he performed was building a masjid to be the court of worship, the school of knowledge, and the starting point for the army's march. Muslims assemble in masjids five times a day, the rich and the poor, the emir and the commanded, the young and the old, side by side, feeling condolence, affection, and intimacy, and visit one another, and at the end of the week, Friday sermon shall have a great impact in their souls.
In masjids, knowledge sessions from which thousands of scholars were graduated are held; sessions of teaching the Glorious Qur'an, lectures of knowledge, and speeches are established.
Allah (Glory be to Him) explained that one of the greatest crimes is blocking the way of people when they want to go to masjids and endeavoring to ruin them. The retribution of such action is disgrace in this world and a great torment in the Hereafter. Allah (may He be Exalted) says: "And who are more unjust than those who forbid that Allâh's Name be glorified and mentioned much (i.e. prayers and invocations, etc.) in Allâh's mosques and strive for their ruin? It was not fitting that such should themselves enter them (Allâh's Mosques) except in fear. For them there is disgrace in this world, and they will have a great torment in the Hereafter." [Surat Al Baqarah: 114].
Masjids are the most beloved spots to Allah. Imam Muslim reported in his Sahih from the Hadith of Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace be upon him) said: "The parts of land dearest to Allah are its mosques, and the parts most hateful to Allah are markets." 
An-Nawawy (may Allah bestow mercy on his soul) said: The dearest parts to Allah are masjids because they are dedicated for mentioning Allah and spots that are established for piety and righteous work. Masjid locations are spots for the descent of the mercy and favor of Allah, whereas markets are on the opposite. 
It was reported in Sahih Al Bukhari and Sahih Muslim on the authority of Abu Hurayrah that the Prophet (peace be upon him) said: "Allah will give shade to seven kinds of people on the Day when there will be no shade but His."
And mentioned among them: "A man whose heart is attached to the mosque."  Masjids are the homes dedicated for worshipping Allah and whoever enters them shall be the guest of Lord. So, there is no heart more kind or a soul happier than a man entertained by his Lord, in His Home, and under His Care. Abu Nu`aym reported in Hilyat Al Awliya' from the Hadith of Abu Ad-Darda' who narrated that the Messenger of Allah (peace be upon him) said: "Masjid is the house of every pious. Allah has undertaken to bestow mercy on those who consider masjids as their homes, and easiness of passing the Sirat (a fine bridge on Hell-Fire) to the pleasure of Allah and to Paradise." 
This hospitality is gained in the world by showering them with peacefulness, happiness, and rest, and in the Hereafter they shall be given dignity and honor in Paradise. Al Bukhari and Muslim reported from the Hadith of Abu Hurayrah (may Allah be pleased with him) who narrated that the Prophet (peace be upon him) said: "Allah will prepare for him who goes to the masjid (every) morning and in the afternoon (for the congregational Salah) an honorable place in Paradise with good hospitality for (what he has done) every morning and afternoon goings."
Praise be to Allah, the Lord of the worlds [i.e., people]. May Allah send His Peace and Blessings upon our Prophet Muhammad, his family, and all his Companions!
 Al Bukhari No. 450, and Sahih Muslim No. 533.
 Al Bahr Az-Zakhkhar (13/ 484) No. 7289, and Al Albany graded it as authentic in Sahih Al Jami` As-Saghir No. (3602).
 (43/ 397) No. 26386, The verifiers of the Hadith said: An authentic Hadith.
 Sahih Al Bukhari No. 458, and Sahih Muslim No. 956.
 Sahih Ibn Khuzaymah 2/ 272 No. 1299.
 Sahih Al Bukhari No. 855, and Sahih Muslim No. 564 with his own wordings.
 No. 568.
 No. 1321.
 Sunan Abu Dawud No. 670, Al Albany said: Weak. However, it is authentic without the story of the questioner. See: The series of weak Hadiths No. 1458.
 Al Fatawa (22/ 206).
 (19/ 372) No. 12379, the verifiers of the Hadith said: Its chain of transmission is authentic according to the conditions of Muslim.
 No. 448, and Al Albany graded it as authentic in Sahih Sunan Abu Dawud (1/ 90) No. 431.
 Sahih Al Bukhari, the book of Salah, chapter on building of masjid, No. 62.
 Sunan Sa`id ibn Mansur (2/ 486) No. 165, Sheikh Sa`d Al Humayd said: The Hadith is good by virtue of other ways, but it is reported from the Companions who narrated it such as Abu Hurayrah, Abu Ad-Darda', and Abu Dhar. As for attributing it to the Messenger of Allah (peace be upon him), it is not valid. [Sunan Sa`id ibn Mansur (2/486-491)].
 No. 446.
 Protecting onself from heat and cold [An-Nihayah Fi Gharib Al Hadith (4/206)].
 Sahih Al Bukhari, the book of Salah, chapter on building of masjid.
 Sahih Al Bukhari, the book of Salah, chapter on building of masjid.
 Camel of great hump.
 No. 803.
 No. 2699.
 No. 671.
 Commentary of Sahih Muslim by An-Nawawy, (2/ 584) briefly and with paraphrase.
 Sahih Al Bukhari No. 1423, and Sahih Muslim No. 1031.
 Hilyat Al Awliya' (6/ 176), and Al Mundhiry said in his book At-Targhib Wat-Tarhib (1/ 298): Reported by At-Tabarany in Al Mu`jam Al Kabir and Al Awsat, and Al Bazzar said: Its chain of narration is good. Al Albany graded it as authentic in the series of authentic Hadiths No. 716.
 Sahih Al Bukhari No. 662, and Sahih Muslim No. 669 with his own wordings.
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