Nasai

695. Commentary: Since the Messenger of Allah (sallallahu alayhi wa sallam) is the last Prophet, then necessarily, his mosque will be the last mosque to have been built by the hand of any Prophet. The qiblah of the Muslims is the very first mosque, which was built by the first Prophet, and the center of the Muslims is the very last mosque, which was built by the last Prophet. What a remarkable virtue! And this virtue will remain until the Day of Resurrection. [ديكهيے فوائد حديث : 692]

Hadith Commentary:
By "my mosque" is meant the Prophet's Mosque (Masjid al-Nabawi).
The indication of the esteemed Imam (rahimahullah) is precisely that one should undertake a journey (shadd al-rihal) for the visitation of the Prophet's Mosque, and whoever goes there will inevitably also attain the blessings of sending salutations and peace (salat wa salam) upon the Noble Messenger (sallallahu alayhi wa sallam) and the two esteemed Companions (al-Shaykhayn: Abu Bakr and Umar, radi Allahu anhuma).

Hadith Commentary:
(1)
By "my mosque" is meant the Prophet’s Mosque (Masjid Nabawi).
Imam Bukhari rahimahullah’s indication is precisely that one should undertake a journey to visit the Prophet’s Mosque.
Then, whoever is granted this honor will also have the opportunity to visit the blessed grave of the Messenger of Allah sallallahu alayhi wa sallam, as well as send salutations and peace upon him, and will also be blessed to send salutations at the graves of the two Shaykhs (Abu Bakr and Umar radi Allahu anhuma).
Some people from previous nations used to travel long distances to visit Mount Tur and the blessed grave of Prophet Yahya alayhis salam, but the Messenger of Allah sallallahu alayhi wa sallam designated only three places for visitation.
Other than these, traveling to Ajmer, Sehwan, Baghdad, or Karbala is not permissible according to the Shariah.
And Allah knows best.

(2)
Ibn Hajar rahimahullah writes:
The commentator of Bukhari, Ibn Battal, has written that in the words of the hadith “except for the Sacred Mosque (Masjid al-Haram),” there are three possible interpretations:
That the Sacred Mosque is equal to the Prophet’s Mosque, or superior to it, or inferior to it. The first position, that it is equal, appears to be the strongest, because to consider it superior or inferior requires evidence.
Perhaps he was not aware of the hadith in which it is clarified that performing prayer in the Sacred Mosque is equal to one hundred thousand prayers, in the Prophet’s Mosque is equal to one thousand prayers, and in Masjid al-Aqsa is equal to five hundred prayers.
This narration has been mentioned by Imam Bazzar in his Musnad and Imam Tabarani in his Mu’jam.
(Fath al-Bari: 3/87)
Therefore, the position of Ibn Battal is weak.
Imam Nawawi rahimahullah has written that the worshipper should strive to pray in that part of the Prophet’s Mosque which was built by the Messenger of Allah sallallahu alayhi wa sallam himself, because the words “my mosque” in the hadith refer specifically to that area.
However, there is consensus among the scholars of the Ummah that the mentioned virtue includes the entire present-day expanded mosque.
It should be noted that during the blessed era of the Messenger of Allah sallallahu alayhi wa sallam, the Prophet’s Mosque was built from unbaked bricks, its roof was made from palm branches, and its pillars were trunks of date palms.
(Sahih al-Bukhari, Manaqib al-Ansar, Hadith: 3906)
When the Messenger of Allah sallallahu alayhi wa sallam returned from the Battle of Khaybar, the Prophet’s Mosque was expanded for the first time because the number of Muslims had increased.
The Messenger of Allah sallallahu alayhi wa sallam increased its width by forty cubits and its length by thirty cubits, but the qiblah wall remained at its original boundary.
When the date palm trunk pillars from the Prophetic era became hollow, Abu Bakr al-Siddiq radi Allahu anhu replaced them.
For complete information regarding the expansions of the Prophet’s Mosque, studying “Atlas Sirat Nabawi” (pp. 160 to 165, Darussalam edition) will be beneficial.

Benefits and Issues:
➊
The most virtuous mosques in the world are three:
Al-Masjid al-Haram, within which is the Ka'bah;
Al-Masjid an-Nabawi; and Al-Masjid al-Aqsa. Therefore, it is permissible and a meritorious act to travel with the intention of visiting these three mosques and worshipping there.
It is not permissible to travel to any other place, mosque, shrine, etc., with the intention that the reward for worship there will be greater.
For indeed, it is prohibited to perform prayer in graveyards,
and the reward for all other mosques is equal.
Therefore, there is no benefit in traveling for this purpose.
However, the virtue of Masjid Quba is also established from other ahadith.
Therefore, this is the fourth mosque,
for which, while being in Madinah, it is recommended (mustahabb) to go for visitation.

➋
The reward for one prayer in Al-Masjid an-Nabawi is equal to one thousand prayers.
Therefore, when the opportunity arises to visit Madinah Sharif,
one should strive to perform as many congregational prayers as possible in Al-Masjid an-Nabawi (sallallahu alayhi wa sallam).
There is no condition to complete forty prayers in this.

➌
In some narrations, the reward for one prayer in Al-Masjid an-Nabawi (sallallahu alayhi wa sallam) is mentioned as equal to fifty thousand prayers,
for example, Sunan Ibn Majah, Hadith: 1413.
However, this hadith is weak.

Hadith Authentication: [وأخرجه البخاري 1190، من حديث مالك به]
Jurisprudential Explanation:
➊ Compared to all other mosques, performing one prayer in the Prophet’s Mosque (Masjid Nabawi) earns the reward of one thousand prayers, except for the Sacred Mosque (Masjid al-Haram, the Ka‘bah), because in the Sacred Mosque, the reward for one prayer is more than one hundred thousand prayers. See: [سنن ابن ماجه 1406، و سنده صحيح]
It is narrated from Sayyiduna Abdullah ibn al-Zubayr radi Allahu anhu that the Messenger of Allah sallallahu alayhi wa sallam said: «صلاة فى مسجدي هذا افضل من الف صلاة فيما سواه من المساجد الا المسجد الحرام، وصلاة فى المسجد الحرام افضل من مائة صلاة فى هذا .» In comparison to other mosques, prayer in this mosque of mine is a thousand times superior, except for the Sacred Mosque, and prayer in the Sacred Mosque (Ka‘bah) is a hundred times superior to prayer in this mosque of mine. [مسند أحمد 5/4 ح 16117، و سنده صحيح و صححه ابن حبان : 1620]
➋ The reward for prayer in the Sacred Mosque is greater than that in the Prophet’s Mosque.
➌ Those who claim that Madinah is superior to Makkah have no evidence for this, and it is better to remain silent regarding such matters and to avoid useless speech.
➍ The Messenger of Allah sallallahu alayhi wa sallam stood at Hazwarah (a place in Makkah) and said: «والله ! إنك لخير أرض الله وأحب أرض الله إليّ، والله ! لو لا أني أخرجت منك ما خرجت .» By Allah! You are the best of Allah’s land and the most beloved of Allah’s land to me. By Allah! Had I not been driven out from you, I would never have left. [سنن ابن ماجه : 3108 وسنده صحيح، وصححه الترمذي : 3925 وابن حبان : 3700 والحاكم عليٰ شرط الشيخين ووافقه الذهبي]
➎ The House of Allah (Masjid al-Haram) and the Prophet’s Mosque (Masjid Nabawi) are two such places where the reward for prayer is greater than in other mosques, and in some narrations, Bayt al-Maqdis (al-Aqsa Mosque) is also mentioned. However, to fabricate and spread among the public that prayer in Ajmer or Raiwind earns greater reward is absolutely false and rejected.

Benefit:
In this hadith, the virtue of performing prayer in the Prophet’s Mosque (Masjid Nabawi) and the Sacred Mosque (Masjid al-Haram) is mentioned. The reward for performing prayer in the Prophet’s Mosque is equal to the reward of one thousand (1000) prayers.