Tirmidhi

English Commentary:
1:
Hafiz Ibn Hajar states in Fath al-Bari:
“Bishr ibn Umar al-Zuhri has clarified in his narration from Rifa‘ah ibn Yahya that prayer was Maghrib (the sunset prayer).” This narration refutes those who have interpreted it as referring to a supererogatory (nafl) prayer.
However, from other narrations it is evident that the Companion uttered these words when rising from bowing (ruku‘), and it was at that moment that he sneezed as well.
The reconciliation and synthesis of all the authentic narrations and the statements of the scholars on this matter is that if one sneezes during prayer, instead of saying ((al-hamdu lillah)) aloud, he should say it silently in his heart.

Note:
(The chain is hasan,
but due to supporting evidence, the hadith is sahih.)

Hadith Commentary:
(1)
It is understood from the narrations that the person who uttered the mentioned words was the very narrator of the hadith, Hazrat Rifa‘ah bin Rafi‘ radi Allahu anhu. Furthermore, this hadith shows that the tasmi‘ (saying “Sami‘a Allahu liman hamidah”) is the prescribed act (wazifah) of i‘tidal, that is, the standing position (qawmah), whereas in the hadith of Abu Hurairah radi Allahu anhu, it is described as the prescribed act of transition (wazifah of intiqal), and this is also the well-known view.
The reconciliation is as follows: When the Messenger of Allah sallallahu alayhi wa sallam began to rise from bowing (ruku‘), he started saying “Sami‘a Allahu liman hamidah,” and its completion occurred in the standing position (qawmah).
(Fath al-Bari: 2/369, 370) (2)
It is understood from this hadith that it is permissible to add non-transmitted (ghayr ma’thur) remembrances (adhkar) in prayer, provided they do not contradict the prescribed (masnun) remembrances.
Hafiz Ibn Hajar rahimahullah has also adopted this position.
(Fath al-Bari: 2/371)
However, the correct view is that in these circumstances, doing so is not permissible; rather, during the time of Prophethood, it was allowed because it was the period of the descent of revelation (wahy), and falsehood could not persist in the guise of truth. But after the cessation of revelation, when the Shari‘ah has been completed, the addition of such words in acts of worship that are not established from the Shari‘ah is questionable.

773. Commentary:
The hadith of Malik refers to the previously mentioned hadith number [769] with «قعنبي عن مالك», from which it is understood that if one sneezes during prayer, then reciting the mentioned supplication or saying «الحمد لله» is permissible. By combining both these hadiths (i.e., Sunan Abi Dawud hadith numbers 770 and 773), it becomes apparent that perhaps the time of rising from bowing (ruku‘) and the occurrence of sneezing was the same, at which point Rifa‘ah radi Allahu anhu uttered these words.

770. Commentary:
It is recommended (mustahabb) to recite the aforementioned supplication after rising from bowing (ruku‘).
However, for all followers (muqtadis) to recite it aloud together is not established from the Companions (radi Allahu anhum ajma‘in). Therefore, obligating all followers to say these words aloud is not correct, nor is this established by this hadith. From this hadith, only the virtue of these words and the affirmation of reciting them at this occasion is proven, not that all followers should recite them aloud. Also, see Sunan Abi Dawud, hadith [773].

932. Commentary:

➊ The timing of sneezing and raising the head from bowing (ruku‘) was the same, as is explicitly stated in Sahih al-Bukhari. See: [صحیح البخاري ، الأذان ، حدیث : 799]

➋ Sneezing is also a blessing from Allah, as it clears the mind and refreshes the body. Therefore, one should express gratitude to Allah. For this, saying “alhamdulillah” is sufficient. If one adds more, there is no harm, as is mentioned in this narration.

➌ Not responding the first time was due to the fear that perhaps I had made a mistake.

➍ This narration is used as evidence that it is permissible to say “alhamdulillah” aloud upon sneezing during prayer. And Allah knows best.

➎ When the imam notices something new among his followers, he should inquire about it and inform the followers of the actual situation.

➏ If someone sneezes during prayer and says “alhamdulillah,” no response should be given to him, because neither the Messenger of Allah (sallallahu alayhi wa sallam) nor any of the Companions responded to that man. If someone does respond, his prayer will become invalid. And Allah knows best.

➐ From this blessed hadith, the virtue of the mentioned remembrance (dhikr) is also evident, that Allah greatly loves this remembrance.

1063. Commentary:

➊ In these narrations, there is neither a negation nor an affirmation of saying «سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ» for the follower (muqtadi); therefore, it is necessary to refer to other detailed narrations, as has already been mentioned under the benefits of Hadith 1063.

➋ Some individuals have deduced from this narration that these words should be said aloud, but it is astonishing that they have overlooked the practice of the Messenger of Allah (sallallahu alayhi wa sallam) and the eminent Companions (radi Allahu anhum), who used to recite them quietly, and instead have based their argument on the incidental action of a single Companion. Whereas, it is more likely that this action occurred from that Companion unintentionally or coincidentally. If this had been the general practice, why would the Messenger of Allah (sallallahu alayhi wa sallam) have inquired about it? Therefore, these words should be said quietly.

Hadith Authentication: [وأخرجه البخاري 799، من حديث مالك به]
Jurisprudential Points:
➊ After bowing (ruku‘), it is permissible to say both «رَبَّنَا وَلَكَ الْحَمْد» and «رَبَّنَا لَكَ الْحَمْد», as established by other narrations, but it is better to recite «رَبَّنَا وَلَكَ الْحَمْدُ، حَمْدًا كَثِيْرًا طَيِّبًا مُبَارَكًا فِيْهِ», as its reward is much greater.
➋ Whether one is the imam or a follower, everyone should say «سَمِعَ اللهُ لِمَنْ حَمِدَهُ» and «رَبَّنَا وَلَكَ الْحَمْدُ» etc., as established by other evidences. See [سنن الدارقطني 1/339، 340، ح1270، وسنده حسن]
➌ Ijtihad (independent juristic reasoning) is permissible.
➍ Remembrance (dhikr) does not invalidate the prayer, even if that remembrance is done based on one’s own ijtihad, provided it does not contradict the Book and the Sunnah.
➎ Allah, the Exalted, would show His Prophet (sallallahu alayhi wa sallam) the angels, while ordinary people could not see them.
➏ Despite hearing a voice, not recognizing the person and then asking others about him is evidence that the Prophet (sallallahu alayhi wa sallam) did not possess knowledge of the unseen (ghayb).