Among the rulings concerning the mosque in Islam, and that one of the signs of the Hour is boasting in mosques and their decoration.

The Shaykh : ... its camel, what remains in the mosque ... because in the system of Islam, it is not permissible to build mosques with leisure, grandeur, beauty, and decorations in them. Rather, this is a method we received from among the customs of the disbelievers. They build churches and the houses they claim to worship Allah in with a structure that has grandeur and beauty. Why? Because they do not have the high spiritual meanings in these houses built for the worship of Allah — they claim! — that attract people to these houses. And so, over time, as the Europeans expanded their embellishment by every means, the matter reached the point where they were not satisfied with decorating the churches with the decoration in which the Europeans excelled. So they needed to resort to new means to attract people to prayer on their day of Sunday. So they began to allow women to enter in their most beautiful adornment and the greatest display of adornment a woman among them could have. They even allowed free mixing and perhaps dancing in what? In the churches that were built, in their claim, for the worship of Allah (Mighty and Majestic)!
So mosques and music, since ancient times, mosques must be built with the shortest construction and the building must be as far as possible from adornment and ostentation. Therefore, when 'Umar ibn al-Khattab (may Allah be pleased with him) expanded the Prophet's Mosque, he said to the builder: "Shelter the people from the heat and the cold, and do not make it red or yellow." Stay away from adornment; just make a shelter where the worshippers can take refuge and be saved from the severity of the heat and the cold.
And the Messenger (peace be upon him) indicated this by his saying: , and Ibn 'Abbas, who is the narrator of the hadith, said: "You will certainly decorate them just as the Jews and the Christians decorated them." And this is fully verified by reality today. For we hardly find a mosque being built except that ... those in charge of it compete to make it more beautiful than such-and-such a mosque, and more radiant than such-and-such a mosque. So the Messenger of Allah (peace be upon him) told the truth: .
And the Umayyad Mosque is with us, and perhaps you have a mosque like it, but one close to it in adornment and decoration. The Umayyad Mosque with us in the Levant is the Ka'bah of the disbelievers; they make pilgrimage to this mosque to study the inscriptions that were decorated on its walls and ceilings with the stone known as mosaic. So the disbelievers come to a house of the houses of Allah; not to worship Allah, but for entertainment and leisure!! Is this how the mosques of Islam are to be built?! No, this is part of the deviation that befell the Muslims in their understanding of aspects of their religion.
So the summary is: there should be no trees in the mosques that are built in the Islamic way, no gardens, no flowers; no, these — also — are to be kept away from the mosques, because they are a source of amusement and adornment from the adornment of worldly life. As for the mosque, it must be in a state such that when the heedless person with the hard heart enters it, he becomes alert and awakens, and he is seized with trembling and fear of Allah (Blessed and Exalted is He). So he prays, and there are no embroidered, decorated carpets before him, nor decorated walls in front of him. Not even the noble verses are permissible to be written on these walls because they distract the worshipper. Therefore, he (peace and blessings be upon him) said, as in "Sahih al-Bukhari," after he prayed one day in a garment with a pattern resembling ... long red, green, white, and blue lines, and so on. This garment is called "anbijaniyyah." So he prayed one day in this garment, and then he (peace be upon him) said after he prayed.
Huh?

Another questioner : ... .

The Shaykh : Yes, a khamisah. This garment is called a khamisah. So after he prayed, he said: , in the narration of al-Bukhari: , but in the narration of "al-Muwatta" — which is more correct in terms of meaning —: .
And when the Messenger of Allah (peace and blessings be upon him) entered the interior of the Ka'bah, he found there the two horns of the ram of Isma'il, the ram of Isma'il whom his father Ibrahim (peace and blessings be upon them) sacrificed. The disbelievers had inherited these two horns from the ram of redemption for Isma'il, and they had placed them as ancient artifacts in the interior of the Ka'bah. So when the Messenger (peace be upon him) entered and prayed, he said: from takhmir; meaning covering. Cover these two horns. Why? So that he would not be distracted by looking at them from the humility before Allah (Blessed and Exalted is He). So look at how eager the Messenger of Allah (peace and blessings be upon him and his family) was to ensure that when a Muslim enters a place, that place is sanctified from anything that distracts and occupies the mind of the worshipper. Look at this from one aspect, and look at the reality of the Muslims today in their mosques from another aspect, and it will become clear to you another miracle of the Messenger (peace be upon him), a scientific and unseen miracle, in addition to the previous miracle: . It will become clear to you another miracle, which is his saying (peace and blessings be upon him): . It was said: Who are they, O Messenger of Allah? He said: . These are the hadiths of the Messenger (peace be upon him); rather, those are the signs of Allah in the Qur'an and in the hadiths of the Messenger (peace be upon him) in affirming the attribute of elevation for Allah (Mighty and Majestic). And these hadiths are regarding how to build mosques. So look at how few are those who obey these hadiths, rather these verses, and follow them? They are the few, .
They are the strangers whom the Messenger (peace be upon him) mentioned in the previous hadith: . In another hadith, that question came: Who are these strangers? He said: but people of evil, from those few, .
So mosques must be kept away from decorations and adornment. So the problem of flowers is a problem sentenced to death from the start. But if we assume that there is a fruit on a tree that has fruit, the matter is as we detailed earlier, and it is not permissible to ...