Surah At-Tawba (9) — Ayah 108

108. (O Prophet!) Never stand in that (mosque) for prayer. A mosque founded from the first day on piety [121] is more worthy that you should stand in it. In it are people who love to purify themselves, and Allah loves those who purify themselves.

[121]
Which Mosque is Built Upon Taqwa?

Which mosque was it and under what circumstances was it built? For clarification, consider the following ahadith:
1. Sayyiduna Abu Sa‘id Khudri ؓ says that two men disputed about which mosque was founded upon taqwa from the very first day. One said it was the Mosque of Quba, and the other said it was the Mosque of the Messenger of Allah ﷺ. Then the Prophet ﷺ said, “It is this mosque of mine.” [ترمذي۔ ابواب التفسير]
2.
The Construction and Later Expansion of Masjid Nabawi:

Sayyiduna Anas ؓ narrates that when the Prophet ﷺ arrived in Madinah, he stayed in the elevated part of Madinah with the tribe of Banu ‘Amr bin ‘Awf. He stayed there for twenty-four (and according to another narration, fourteen) nights. Then he sent for Banu Najjar, who came with their swords hanging. The Prophet ﷺ mounted his she-camel, Sayyiduna Abu Bakr Siddiq ؓ was with him, and the chiefs of Banu Najjar surrounded him. From there, the Prophet ﷺ went and stayed at the house of Abu Ayyub. The Prophet ﷺ liked that wherever the time for prayer came, he would pray there, and he even prayed in the sheep pens. Then the Prophet ﷺ ordered the construction of the mosque. He called the chiefs of Banu Najjar and said, “Set a price for this garden of yours with me.” They replied, “No, by Allah, we will take its price only from Allah, the Exalted.” In that garden, there were some graves of polytheists, some ruins, and some date-palm trees. Then the Prophet ﷺ ordered that the graves of the polytheists be dug up, the ruins leveled, and the date-palm trees cut down and their wood set up towards the qiblah. On both sides, stone embankments were made. The Companions were carrying stones while reciting poetry, and the Prophet ﷺ was also reciting poetry with them and saying:
«اللہم لاخير الا خيرالاٰ خرة»
«فاغفر الانصار والمهاجرة»
(O Allah! The real goodness is the goodness of the Hereafter. O Allah, forgive the Ansar and the Muhajirin.) [بخاري۔ كتاب الصلوة۔ باب هل ينبش قبور مشركي الجاهليه]
3. Abu Sa‘id Khudri ؓ says that (at the time of the construction of Masjid Nabawi) we were each carrying one brick, and ‘Ammar ؓ was carrying two bricks. The Prophet ﷺ saw ‘Ammar ؓ and began to dust the dirt off his body and said, “Alas! A rebellious group will kill ‘Ammar ؓ. He will call them to Paradise, and they will call him to Hellfire.” Thus, ‘Ammar ؓ used to say: I seek refuge with Allah from tribulations. [بخاري۔ كتاب الصلوة۔ باب التعاون فى بناء المسجد]
4. ‘Abdullah bin ‘Umar ؓ says that in the time of the Prophet ﷺ, Masjid Nabawi was built of unbaked bricks, its roof was of palm branches, and its pillars were of palm wood. Sayyiduna Abu Bakr Siddiq ؓ did not add anything to it (during his caliphate), and Sayyiduna ‘Umar ؓ expanded the mosque but kept the building as it was in the time of the Prophet ﷺ, that is, of bricks and palm branches. However, the palm wood pillars were replaced. Then Sayyiduna ‘Uthman (may Allah be pleased with him) changed it, greatly expanded it, had its walls built of decorated stone and plaster, its pillars of decorated stone, and its roof made of teak wood. [بخاري۔ كتاب الصلوة۔ باب بنيان المسجد]