IT IS MUSTAḤABB to remember Allah abundantly and to say tasbīḥ, tahlīl, taḥmīd, takbīr and other adhkār. It is also mustaḥabb to recite Qur’ān abundantly, to read hadiths of the Messenger of Allah 
, and to study jurisprudence and all other sciences of the Sharī‘ah. Allah 
says: “In houses which Allah has permitted to be erected, and His Name to be exalted therein, and in which He is glorified in the morning and in the evening, by men. . ..” [1].
, and to study jurisprudence and all other sciences of the Sharī‘ah. Allah says: “In houses which Allah has permitted to be erected, and His Name to be exalted therein, and in which He is glorified in the morning and in the evening, by men. . ..” [1].
Allah says: “And whoever honours the symbols of Allah, that comes from piety of the heart.” [2].
says: “And whoever honours the symbols of Allah, that comes from piety of the heart.” [2].
Allah also says: “Whoever honours that which Allah has made sacrosanct, it is best for him in the sight of his Lord.” [3].
also says: “Whoever honours that which Allah has made sacrosanct, it is best for him in the sight of his Lord.” [3].
We relate from Buraydah 
that the Messenger of Allah said: “Mosques were only built for what they were built for.” [4].Muslim related it in his Ṣaḥīḥ.
that the Messenger of Allah said: “Mosques were only built for what they were built for.” [4].Muslim related it in his Ṣaḥīḥ.We relate from Anas that the Messenger of Allah told the Bedouin man who urinated in the mosque: “These mosques are not suitable places for any of this urination or filth. They are only [meant] for the remembrance of Allah , [ṣalāh], and the recitation of the Qur’ān,” [5].or however it was the Messenger of Allah said it. Muslim narrated this in his Ṣaḥīḥ.
that the Messenger of Allah told the Bedouin man who urinated in the mosque: “These mosques are not suitable places for any of this urination or filth. They are only [meant] for the remembrance of Allah , [ṣalāh], and the recitation of the Qur’ān,” [5].or however it was the Messenger of Allah said it. Muslim narrated this in his Ṣaḥīḥ.It is imperative for anyone sitting in the mosque to make the intention for I‘tikāf. This is valid, in our [Shāfi‘ī] opinion, even if one only stays for a moment. One of our colleagues says that I‘tikāf is valid even if one simply enters the mosque and passes through it without staying at all. Anyone passing through [a mosque] ought to make the intention for I‘tikāf so that he may gain the merit of it, according to this person. It is best to stand for a while and then pass on. Anyone sitting in the mosque ought to enjoin whatever good he sees and prevent whatever evil he sees. We are enjoined to do this in places other than the mosque, so in the mosque it is even more essential in order to protect, glorify, dignify and honour it. Our [Shāfi‘ī] colleagues hold that if one enters the mosque but is unable to perform the ṣalāh of greeting the mosque, because of impurity, being busy or any other reason, he should say four times: Glory be to Allah, all praise is due to Allah, there is no god but Allah and Allah is greater. Such was the opinion of one of our righteous predecessors, and there is no harm in it.
Subḥāna-llāh, wa-l-ḥamdu li-llāh, wa lā ilāha illa-llāh, wa-llāhu akbar.
References
[1] Qur’ān 24:36.
[2] Qur’ān 22:32.
[3] Qur’ān 22:30.
[4] Muslim (569).
[5] Muslim (284).