Bukhari

Hadith Commentary:
The narration from Qadi Shurayh was connected by Mu‘ammar, from Ayyub, from Ibn Sirin, from Qadi Shurayh, that when he would pass judgment regarding a right owed by someone, he would order that the person be detained in the mosque until he fulfilled the obligation upon him.
If he fulfilled it, then good; otherwise, he would be sent to prison.
This is similar to how, nowadays, courts issue orders for detention until the court session concludes.
The incident regarding Thumamah (radi Allahu anhu) occurred on the 10th of Muharram, 6 AH.
He was captured as a prisoner of war.
However, the Messenger of Allah (sallallahu alayhi wa sallam), out of kindness, set him free, the effect of which was that he accepted Islam.

Hadith Commentary:
The details of the narration of Thumamah bin Uthal radi Allahu anhu are as follows: In Muharram of the 6th year of Hijrah, the Messenger of Allah sallallahu alayhi wa sallam dispatched a detachment of thirty noble Companions radi Allahu anhum ajma‘in under the leadership of Muhammad bin Maslamah radi Allahu anhu towards the region of Najd.

They saw some people heading towards Madinah Tayyibah. The noble Companions radi Allahu anhum ajma‘in intercepted them and captured their leader, Thumamah bin Uthal radi Allahu anhu. He was then brought to Madinah Munawwarah and tied to a pillar of the mosque.

The Messenger of Allah sallallahu alayhi wa sallam came and asked Thumamah:
“O Thumamah! What do you think?” He replied, “My opinion is good. If you kill me, you will be killing one whose blood will be avenged. If you show kindness, you will be showing kindness to one who is grateful. And if you desire wealth, then ask whatever you wish, it will be presented to you.”
Upon hearing this reply, the Messenger of Allah sallallahu alayhi wa sallam left.

The same question and answer took place the next day.
The same happened on the third day as well.
Then the Prophet sallallahu alayhi wa sallam ordered that Thumamah be released, so he was set free.

He immediately went to a garden near the mosque, performed ritual bath (ghusl), and came into the mosque. Then he said:
“I bear witness that there is no deity worthy of worship except Allah, and I bear witness that Muhammad is the Messenger of Allah.”

Then he said:
“O Muhammad (sallallahu alayhi wa sallam),
By Allah! There was no one on the face of the earth more hateful to me than you, but now you are the most beloved to me.
By Allah! There was no religion more detestable to me than your religion, but now your religion is the most beloved to me.
By Allah! There was no city more disliked by me than your city, but now your city is the most beloved to me of all cities.
When your horsemen captured me, I was intending to perform ‘umrah. What do you command regarding this?” The Messenger of Allah sallallahu alayhi wa sallam congratulated him and instructed him to perform ‘umrah. Thus, he went to Makkah Mukarramah for ‘umrah. Someone said to him, “Have you become irreligious?” He replied, “No, rather I have believed in Muhammad sallallahu alayhi wa sallam and become a Muslim.
Now I will never return to your religion.
By Allah! Now not a single grain of wheat will come to you from Yamamah, unless the Messenger of Allah sallallahu alayhi wa sallam permits it.”

(Sahih al-Bukhari, al-Maghazi, Hadith: 4372)
From this detailed narration, both aspects of the chapter heading established by Imam al-Bukhari rahimahullah are proven: that a non-Muslim can be detained in the mosque, and the issue of performing ritual bath (ghusl) before embracing Islam is also established.

Benefits and Issues:
➊
It is permissible, due to expediency, to allow a disbeliever to enter or be confined in the mosque.

➋
The excellent acts of worship and noble manners of the Messenger of Allah (sallallahu alayhi wa sallam) and the Muslims made a prisoner of war embrace Islam without any compulsion or coercion.
And this is evidence that Islam did not spread by the force of the sword.

Lexical Explanation:
«خَيْلَا» A squadron of horsemen.
«فَرَبَطُوهُ» They tied him up.
«بِسَارِيَةٍ» Its plural is «سَوَارِي», meaning "pillar." This refers to the prisoner Thumamah bin Uthal radi Allahu anhu. At the time of his capture, he was a disbeliever, but later he became a Muslim.

Benefits and Issues:
➊ From this hadith, it is understood that when necessary, it is permissible for a polytheist to enter the mosque and to keep him detained there.
➋ The wisdom appears to be that the disbeliever and polytheist may witness with their own eyes the Muslims performing prayer, which is one of the pillars of Islam, listen to the recitation of the Qur'an, observe the demonstration of unity and solidarity through the formation of rows, see the rich and poor standing together in the same row with their hands folded, and thus be influenced by these things.
➌ The one who was brought as a prisoner was Thumamah bin Uthal, the chief of Yamamah. He was coming for the purpose of performing 'umrah when he was captured by the Muslims. In the Prophet's Mosque, the Prophet sallallahu alayhi wa sallam had him tied to a pillar for three days; eventually, he entered the fold of Islam.