When entering the Masjid
Enter with the Right ...
When you enter the Masjid, it is from the sunnah to enter with your right leg first. Anas (RA) said: "It is a from the Sunnah when you enter the Masjid to begin with your right foot, and when you leave [the Masjid] to begin with your left foot." (Mustadrak)
And say ...
Abu Humaid (RA) and Abu Usaid (RA), related that the Messenger of Allah (peace and blessings be upon him) said:
"When one of you enters the Masjid, let him say, 'O Allah, open the gates of Your Mercy for me." (Allahumma aftah Ii abwaba rahmatika) (Muslim)
Or "I take refuge with Allah, the Supreme, and with His Noble Face, and His eternal authority from the accursed devil." (A'udhu billahil 'azeem wa biwajhihil kareem wa sultanihil qadeem minashaitanirrajeem.) (Abu Daawood)
Perform Tahiyyatul-Masjid on entrance
When you enter the Masjid, you should first perform two units of prayer, which are called Tahiyyatul-Masjid (which literally means, greeting the Masjid). The Messenger of Allaah (peace and blessings be upon him) said:
"When one of you enters the Masjid, then let him perform two Rak'ahs (units of prayer) before he sits down."(Bukhaaree)
It is the same even if you enter the Masjid at the time the Imaam is given the Khutbah on Jumu'ah day. However, if the congregational salaah is already in progress, you should just join the prayer.
Buying And Selling is not permitted in the Masjids
It is forbidden to buy and sell in the Masjid. A Masjid is not built to be a store or marketplace; instead it is built for the remembrance of Allah, for establishing prayer, for educating Muslims about their religious affairs, and so on. Abu Hurairah (RA) reported that the Messenger of Allah (peace and blessings be upon him) said:
"If you see someone buy or sell in the Masjid, then say, 'May Allah not make your trade profitable."'(Tirmidhee)
Regarding the ruling for buying and selling in rooms or halls that are connected to the Masjid, or halls that are used for prayer, the scholars gave the following' ruling: "If a room is specifically used for prayer, and if it is connected to the Masjid, it is not permissible to buy or sell in it, nor is it permissible to advertise products inside of it. The Prophet (peace and blessings be upon him) indeed said:
'It you see someone buy or sell in the Masjid, then say: May Allah not make your trade profitable ....
As for rooms, thell we need to elaborate. If a room is within the enclosure of a Masjid, then it takes the ruling of a Masjid, and what we said about halls applies to that room. But if the room is outside the Masjid's enclosure, it does not take the ruling of the Masjid, even if there is a door that connects it to the Masjid. This ruling is based on the fact that the Prophet's house, in which 'Aaisha (RA) lived, had a door that was connected to the Masjid, yet his house did not take the same ruling as the Masjid. "
Question: In saying, "May Allah not make your trade profitable," should we distinguish between a person who knows the ruling for trading in the Masjid and a person who doesn't know the ruling?
Answer: The plain meaning of the hadeeth's wording indicates that we should say the phrase both to a person who knows the ruling for trading in the Masjid and to a person who doesn't know the ruling
Announcing lost items is not permissible in the Masjid
Allah's Masjids are built for His remembrance, His glorification, the recitation of the Qur'an, and prayer; they are not built as places where people go to ask about their lost possessions. Abu Hurairah (RA) related that the Messenger of Allah said:
"Whoever hears a person ask or make an announcement ih the Masjid about a lost possession, should say, 'May Allah not return it to you,' for Masjids were not built for this." (Muslim)
Speaking Loudly In The Masjid
While he was In the Masjid,Ka ab Ibn Maalik (RA) asked Ibn Abee Hadrad ! (RA), to pay him back for a loan. In the ensuing discussion, they raised their voices, to the degree that the Messenger of Allah (peace blessings be upon him) heard them, even though he was in his home. He went out to them, uncovering the barrier from his apartment.
He then called out, "O Ka'ab! Ka'ab said, "Here I am, answering your call, O Messenger of Allah (peace and blessings be upon him)" He said:
"Remove (forgive) a part of this debt of yours, "after which he signaled that Ka'ab should forgive Ibn Abee Hadrad for half of the debt. Ka'ab (RA), said, "I have indeed done so, O Messenger of Allah." The Prophet then said to Ibn Abee Hadrad (RA) "Stand and pay him" (Muslim)
In another narration, As-Saaib Ibn Yazeed said, "I was standing in the Masjid when a man pelted me with a small pebble. When I looked around, [I saw that] it was 'Umar Ibn A1-Khattaab (RA). He said, 'Go and bring me these two [men].' I brought them to him, and he said, 'Who are you two?' Or he said, Where are you two from?' They said, 'From the people of Taaif.' He said, 'Had you been from the people of this land, I would have made you feel pain: You raise your voices in the Masjid of the Messenger of Allah' (Bukhaaree).
Reflecting on the two abovementioned narrations, one might conclude that it is Makrooh (disliked) to raise one's voice in the Masjid.
Praying Behind The Men Of The Congregation And Not Mixing With Them
The rows of women in a Masjid are behind the rows of men, and the further a woman is from men, the better it is for her. Abu Hurairah (RA) reported that the Messenger of Allah (peace and blessings of Allaah be upon him) said, "The best of rows for men is the first one, and worst of them is the last one. The best of rows for women is the last one, and the worst of them is the first. (Muslim). However, if the praying area of the women is separate from that of the men, then the best of their rows now becomes the first of their rows.
Even after he finished leading the people in prayer, the Prophet (peace and blessings of A1laah be upon him) made sure that men and women remained separated. When he finished his prayer, he would remain in the spot he prayed in for a short while, so as to allow the women to leave before the men, and to set out to their homes before the men reached them at the entrance of I the Masjid. Umm Salamah (RA), the wife of the Prophet (peace and blessings of Allaah be upon him), related that, "During the lifetime of the Messenger of Allah (peace and blessings of Allaah be upon him), as soon as women would make Tasleem (say 'Assalaamu 'Alaikum Wa-Rahmatullah, ' signaling the end of prayer) from a prescribed prayer, they would stand [to leave]; meanwhile, the Messenger of Allah (peace and blessings of Allaah be upon him) and those men who prayed with him would remain for a period that Allah willed (i.e., for a short while). Then, when the Prophet (peace and blessings of A1laah be upon him) stood up [to leave], the men stood up [as well]." (Bukhaaree).
This is a practice that should be encouraged even today, the men should remain for a short while after the prayer, so as to allow women to leave; and women should not delay but should instead return quickly to their homes.