Bukhari

Hadith Commentary:
The translation of the verse is:
"Guard your prayers, and the middle prayer, and stand before Allah with devotion." (Surah al-Baqarah)

By the "middle prayer," the Asr prayer is meant.

It is evident from the verse that any worldly talk during the prayer is absolutely prohibited.

Hadith Commentary:
(1)
It is understood from this hadith that the prohibition of speaking during prayer was established in Madinah Tayyibah, because Hazrat Zayd bin Arqam (radi Allahu anhu) was an Ansari and had embraced Islam in Madinah Munawwarah. The verse referenced in this hadith is also Madinan. Hazrat Abdullah bin Mas'ud (radi Allahu anhu) also came into the service of the Messenger of Allah (sallallahu alayhi wa sallam) in Madinah Munawwarah and offered greetings while he (sallallahu alayhi wa sallam) was performing prayer. In a narration reported from him, the Messenger of Allah (sallallahu alayhi wa sallam) said:
“In prayer, there should be remembrance of Allah, so stand before Allah with reverence.”
After this, we were commanded to remain silent.
This narration also shows that the prohibition of speaking during prayer was established by this noble verse which is in Surah al-Baqarah.
(Fath al-Bari: 3/97)
(2)
Speaking during prayer out of forgetfulness or due to lack of knowledge does not invalidate the prayer, because it is mentioned in the hadith:
“Allah the Exalted has forgiven my ummah for mistakes and forgetfulness.”
(Sunan Ibn Majah, al-Talaq, Hadith: 2043)
Furthermore, Hazrat Mu'awiyah bin Hakam (radi Allahu anhu) says that once I was performing prayer with the Messenger of Allah (sallallahu alayhi wa sallam) when suddenly a man sneezed during the prayer, so I said “Yarhamuk Allah” (may Allah have mercy on you) during the prayer.
At this, the people began to stare at me.
I said:
“Alas! May my mother lose me, what is the matter? Why are you looking at me angrily?” At this, they began to strike their thighs with their hands, from which I realized that they wanted me to be silent, so I became silent.
When the Messenger of Allah (sallallahu alayhi wa sallam) finished the prayer, may my parents be sacrificed for you! I have never seen a teacher before or after you better in teaching than you. By Allah! You neither scolded me, nor beat me, nor adopted a harsh tone, rather you said gently:
“In prayer, there is no scope for human speech; rather, there should only be glorification (tasbih), magnification (takbir), and recitation of the Qur’an.”
(Sahih Muslim, al-Masajid, Hadith: 1199(537))
From this hadith, it is clearly understood that if someone speaks during prayer out of ignorance, the prayer is not invalidated.
If it were so, the Messenger of Allah (sallallahu alayhi wa sallam) would have ordered that person to repeat the prayer, but he (sallallahu alayhi wa sallam) sufficed with only informing him of the ruling.
And Allah knows best.

1220. Commentary:

➊ “Necessary speech” refers to things like: responding to greetings, supplicating for someone who sneezes, clarifications related to the prayer, etc.—not household conversations or business matters.

➋ “The most virtuous prayer”—It has already been mentioned in Hadith 473 that this refers to the ‘Asr prayer. There are other opinions regarding this, but the preferred view is this one. For details, see: [ذخیرة العقبیٰ شرح سنن النسائي : 6/157-162 ، حدیث : 473]

➌ “The command to remain silent” means refraining from talking to one’s companion, not absolute silence such that remembrances, supplications, or recitation of al-Fatihah would also become prohibited. There is no prayer in which nothing is recited and there is complete silence. However, in congregation, reciting aloud (jahr) is prohibited.

➍ Abrogation (naskh) is established in the Shari‘ah.

➎ Any kind of speech invalidates the prayer.

Commentary:
1:
According to the statement of the Messenger of Allah (sallallahu alayhi wa sallam), forgetfulness and mistakes are pardoned for the believer. Some people have stipulated the condition that "provided it is little." We say that in such a situation, a person is only able to speak a little before he remembers.

949. Commentary:
Speaking during the prayer is forbidden. Except that if, by mistake or forgetfulness, a word slips from the tongue, then it is excused.

Lexical Explanation:
«إِنْ كُنَّا» is the abbreviated form of «إِنْ», meaning it is derived from «إِنَّ» by way of «إِنْ». Its noun is omitted, i.e., «إِنَّا» or «إِنَّهُ». And «كُنَّا» is its predicate.
The “waw” (واؤ) in «وَالصَّلَاةِ الْوُسْطٰي» is for specification here, meaning: especially guard the middle prayer. And according to the most correct opinion, by this is meant the ‘Asr prayer (salat al-‘asr).
«قَانِتِينَ» means: fearful, apprehensive, and remaining silent. “Qunut” has several meanings; the noble Companions (radi Allahu anhum) have taken it here to mean silence. They derived this meaning based on contextual indicators or in light of the explanation of the Prophet (sallallahu alayhi wa sallam).

Benefits and Issues:
➊ This hadith establishes that every kind of conversation and speech is prohibited during prayer (salah).
➋ In the early days of Islam, speaking was permitted, which was later declared prohibited.

Narrator of the Hadith:
(Zayd ibn Arqam radi Allahu anhu) was from the Ansar, specifically from the Khazraj tribe, hence he is called Ansari Khazraji. His kunyah is Abu ‘Amr. He participated for the first time in the Battle of Khandaq. He took part in seventeen expeditions (ghazawat) with the Prophet (sallallahu alayhi wa sallam). At the time of the Battle of Siffin, he was among the supporters of Sayyiduna ‘Ali (radi Allahu anhu), and in fact, was among his close companions. He settled in Kufa and passed away in 66 AH.