Bukhari

Hadith Commentary:
When the Prophet’s Mosque (Masjid Nabawi) was first constructed during the time of the Messenger of Allah (sallallahu alayhi wa sallam), its length and width were thirty square cubits.
Then, after the Battle of Khaybar, due to necessity, its length and width were made fifty square cubits.
During his caliphate, Umar (radi Allahu anhu) reinforced the Prophet’s Mosque with unbaked bricks and palm branches, and the pillars were made of wood.
During his caliphate, Uthman (radi Allahu anhu) had it constructed with solid materials.
After this, when Abu Hurairah (radi Allahu anhu) came to Madinah, he narrated a hadith of the Prophet (sallallahu alayhi wa sallam) that the Messenger of Allah (sallallahu alayhi wa sallam) had foretold that one day his mosque would be constructed on solid foundations.
Upon hearing this hadith, Uthman (radi Allahu anhu), out of happiness, presented Abu Hurairah (radi Allahu anhu) with five hundred dinars.
The later rulers of Islam took an active part in the construction and strengthening of the Prophet’s Mosque.
In the present era, the government of Saudi Arabia (may Allah make it everlasting)
has made the building of the mosque so vast, expansive, and strong that upon seeing it, prayers for this government come forth from the heart.
May Allah accept their noble services.
Based on the ahadith and traditions, it is not good to excessively adorn and embellish mosques.
This was the custom of the Jews and Christians, that they, becoming heedless of the true spirit of their religion, became enamored with outward beauty and adornment.
The same is the condition of Muslims today, whose minarets reach the skies, but they are found empty of tawhid (monotheism), sunnah, and the true spirit of Islam.
Except for whom Allah wills.

Hadith Commentary:
➊
During the blessed era of the Messenger of Allah (sallallahu alayhi wa sallam), the construction of Masjid Nabawi was done with unbaked bricks; palm branches were used for the roof, and palm trunks were used for the pillars.
There are indications in the hadiths that after the conquest of Khaybar, its area was somewhat expanded, but the materials used during the construction remained the same as before.
During the era of Umar (radi Allahu anhu), although there was abundance of wealth, he only added two rows to its length and breadth or towards the qiblah, but the construction materials and style remained as before, i.e., unbaked bricks, a roof of palm branches, and pillars of palm trunks, etc. However, during the caliphate of Uthman (radi Allahu anhu), both the construction materials and style changed.
He purchased the chambers of the Mothers of the Believers (radi Allahu anhunna ajma'in) from his own wealth and included them in the mosque, and increased the length and breadth of the mosque. In addition, instead of unbaked bricks, decorated stones were used, lime was used to join them, and the pillars were also made of stone. For the roof, instead of palm branches, the cuttings of Saagwan (teak) were used.
Objections were also raised against this sincere act of Uthman (radi Allahu anhu), for which he had to answer while standing on the pulpit.
We will explain this in detail under hadith number 4500.
In any case, the length and breadth of the mosque can be increased as needed.
Likewise, there is no objection in using the best and most valuable materials for its strength, and while maintaining simplicity, it can also be made elegant and magnificent.

➋
The muhaddith Ibn Munayyir (rahimahullah) has said that when people start building their personal houses with solid materials and spend money on their adornment and decoration, then in such circumstances, if the same approach is adopted in the construction of mosques, there is no harm in it, so that the mosques are not disrespected.
Hafiz Ibn Hajar (rahimahullah), clarifying this position, said:
If the reason for not adorning the mosque is only to follow the pious predecessors (salaf salihin), then this position is correct. But if the reason for ignoring decoration and adornment is that such embellishment disturbs the humility and submissiveness (khushu' and khudu') of the worshipper, then this position cannot be agreed upon.
(Fath al-Bari: 1/700)
However, we cannot refrain from expressing the reality that in this era of tribulation, people have paid much attention to the adornment and decoration of mosques, especially the use of mirrors and colored tiles to the right and left of the mihrab, and the installation of expensive chandeliers, all of which fall under the category of things from which the Messenger of Allah (sallallahu alayhi wa sallam) forbade. Undoubtedly, the construction of the mosque should be on strong foundations, and there is no objection in making it grand and splendid.
But spending money on adornment is extravagance and wastefulness, which Allah, the Exalted, has forbidden.
The trend of decorating mosques began with Walid ibn Abd al-Malik ibn Marwan; it was the last era of the Companions (radi Allahu anhum ajma'in), and many scholars remained silent at that time due to fear of tribulation.

➌
The expression of dislike from the Messenger of Allah (sallallahu alayhi wa sallam) regarding this adornment and decoration was because it leads to immersion and excessiveness in worldly matters, which causes a person to become heedless of the Hereafter.
Accordingly, Ibn Battal (rahimahullah) has written that prohibition regarding the adornment of mosques is narrated from Umar (radi Allahu anhu).
Perhaps he deduced this from the incident that the Messenger of Allah (sallallahu alayhi wa sallam) returned the decorated cloak of Abu Juhm (radi Allahu anhu) and said that it distracted me from my prayer.
(Sharh Ibn Battal: 2/97)
However, after narrating this incident, Hafiz Ibn Hajar (rahimahullah) wrote that it is possible that Umar (radi Allahu anhu) had some specific instruction regarding this, because in Sunan Ibn Majah it is narrated that Umar (radi Allahu anhu) said: When evil deeds spread among a people, they begin to decorate their places of worship with great adornment. But in its chain of narration is Jabara ibn Mughallis, about whom the imams of criticism and validation have spoken.
(Fath al-Bari: 1/689)
However, in earlier times, if Muslim kings and rulers had not built grand and solid mosques, today in the lands of disbelief, their traces would have been erased, as is the case with the Great Mosque of Cordoba, the monuments of Andalusia, and the mosques of India, etc. Although in the lands of disbelief these mosques lament the loss of Muslims, their continued existence is a sign that once Islam was dominant in these places, and today, due to the weakness of Muslims, the disbelievers have taken over.
(Inna lillahi wa inna ilayhi raji'un)
Some Muslim rulers have marked all the changes that occurred during the Prophetic, Faruqid, and Uthmani eras, distinguishing them, but the subsequent architectural changes are not distinguished from one another.
However, the Turkish style of construction has been distinguished by its color. In the present era, the Saudi government has made the building of Masjid Nabawi so vast and spacious that seeing it fills the heart with joy, and spontaneous prayers for the continuity of this government come from the heart.
May Allah, the Exalted, accept their noble services and make them a means of salvation for them on the Day of Judgment. But in other countries, the minarets of Muslims' mosques may reach the skies, yet these mosques are devoid of the nurturing of tawhid and sunnah, of the true elevation of Islam, and are empty of worshippers.
We pray to Allah, the Exalted, that He makes these mosques centers of tawhid and sunnah and fills them with worshippers.
Amin!

451. Commentary:
Allamah Ibn Battal and others have stated that this narration is evidence that the construction and adornment of mosques should always be done with moderation. Despite the abundance of wealth during the era of Umar radi Allahu anhu due to conquests, he did not alter the mosque; he only replaced the roof branches and decayed pillars. After him, Uthman radi Allahu anhu expanded and beautified it due to its narrowness, but there was no excessiveness in this, even though some Companions criticized him for it. Historically, it is established that Walid bin Abd al-Malik bin Marwan was the first person to adorn mosques, and this was at the very end of the era of the Companions. However, most of the scholars remained silent out of fear of tribulation. [عون المعبود] Some did offer criticism as well.