Bukhari

Hadith Commentary:
(1)
In one narration, it is mentioned that among the noble Companions (radi Allahu anhum) whom Hazrat Salim, the freed slave of Abu Hudhayfah (radi Allahu anhu), used to lead in prayer were Hazrat Abu Bakr as-Siddiq, Hazrat Umar, Hazrat Abu Salamah, Hazrat Zayd bin Harithah, and Hazrat Amir bin Rabi’ah (radi Allahu anhum).
(Sahih al-Bukhari, al-Ahkam, Hadith: 7175)
The presence of Hazrat Abu Bakr (radi Allahu anhu) among them is questionable, because he migrated to Madinah in the company of the Messenger of Allah (sallallahu alayhi wa sallam), whereas according to the narration, this incident took place before the migration.
Imam Bayhaqi has answered this by stating that Hazrat Salim (radi Allahu anhu) used to lead their congregation after the migration, so it is possible that Hazrat Abu Bakr (radi Allahu anhu) was present among them at that time.
And Allah knows best.
Its relevance to the chapter heading is that all the eminent Qurayshi Companions (radi Allahu anhum) preferred him over themselves for leading the prayer, thus the leadership of prayer by a slave is valid. Furthermore, the second part of the chapter title is also established from this: that a slave should not be prevented from leading the prayer without reason.
(Fath al-Bari: 2/241)
It should be noted that Hazrat Salim (radi Allahu anhu) was originally the slave of an Ansari woman, who freed him, but even before his emancipation, he used to lead people in prayer.
After his emancipation, Hazrat Abu Hudhayfah (radi Allahu anhu) adopted him as his son.
That is why he is called Salim, the freed slave of Abu Hudhayfah.
According to the majority, the leadership of prayer by a slave is valid.
Only Imam Malik is reported to have opposed this view.
He stated that a slave should not lead free people in prayer.
However, if he is a scholar and reciter (qari), and the followers are not, then in such circumstances he may be appointed as imam, but even then, he should not be made imam for Jumu’ah (Friday prayer), because Jumu’ah is not obligatory upon a slave.
Allamah Ashhab al-Maliki (rahimahullah) opposed this, stating that even for Jumu’ah, a slave can be made imam, because when he participates in Jumu’ah, the obligation is fulfilled through him.
(Fath al-Bari: 2/239)

(2)
Some scholars have declared the leadership of prayer by a minor (one who has not reached puberty) to be impermissible.
They present a hadith, which Hafiz Ibn Hajar (rahimahullah) has cited from Musannaf ‘Abd al-Razzaq, that a child should not lead the prayer until he reaches puberty, but this narration is weak.
Imam Bukhari (rahimahullah) has narrated in his Sahih an incident that ‘Amr bin Salamah (radi Allahu anhu) used to lead his people in prayer while he was seven years old.
(Sahih al-Bukhari, al-Maghazi, Hadith: 4302)
Hazrat ‘Amr bin Salamah (radi Allahu anhu) states that the Messenger of Allah (sallallahu alayhi wa sallam) said to my father: “When the time for prayer comes, let one of you give the call to prayer (adhan), and let the one who knows the most Qur’an and is most learned among you lead the prayer.”
When my people saw that there was no one more learned or who had memorized more Qur’an than me, they put me forward to lead the congregation.
(Sahih al-Bukhari, al-Maghazi, Hadith: 4302)
Despite this clear hadith, the jurists have differed on this issue.
Imam Bukhari (rahimahullah), refuting them, has established the validity of a child’s leadership in prayer through authentic ahadith.