Bukhari

Hadith Commentary:
Imam Shafi'i rahimahullah has stated in the book Al-Umm that it is Sunnah in prostration (sujud) to keep the elbows separated from the sides and the stomach apart from the thighs.

Hadith Commentary:
(1)
In a narration from Ibn Umar radi Allahu anhu, it is stated: Do not spread your hands on the ground like a predatory animal; place your palms on the ground, and keep your arms apart. When you do so, it is as if all your limbs have performed prostration (sujud).
Similarly, in a narration from Bara’ bin Azib radi Allahu anhu, it is stated: During prostration, place your hands on the ground and raise your elbows.
(Sahih Muslim, Kitab al-Salat, Hadith: 1104 (494))
Hafiz Ibn Hajar rahimahullah has written that from other similar ahadith, it is understood that spreading the arms during prostration is necessary. However, from a hadith in Abu Dawud, it is understood that doing so is recommended (mustahabb), not obligatory.
The words of the hadith are that the Companions radi Allahu anhum complained of the difficulty of prostration due to spreading the arms during sujud, so the Prophet sallallahu alayhi wa sallam said: Take support from your knees, meaning, rest your elbows on them to gain comfort and ease.
Imam Abu Dawud has titled this as follows:
Permission to leave off spreading (the arms), (Sunan Abi Dawud, Kitab al-Salat, Hadith: 902; Fath al-Bari: 2/381)
However, this permission is in the case of an excuse, that is, when one is tired due to the length of the prostration, one may take support from the knees. But in normal circumstances, the arms should be kept apart from the sides during prostration.
Imam Tirmidhi rahimahullah has interpreted the instruction to take support from the knees as referring to rising for standing after completing the prostration.
Imam Tahawi rahimahullah has interpreted it as taking support from the knees when going into prostration after standing.
In summary, these are four separate situations, the details of which are as follows:
➊ Imam Bukhari rahimahullah has described the correct manner of prostration for normal circumstances.
➋ Imam Abu Dawud rahimahullah has mentioned the permission to rest the elbows on the thighs in case of an excuse.
➌ Imam Tirmidhi rahimahullah has described taking support from the knees when rising after completing the prostration.
➍ Imam Tahawi has mentioned taking support from the knees when going into prostration after standing.
(2)
Imam Bukhari rahimahullah has stated at the end of the hadith that Layth has also narrated from Ja‘far bin Rabi‘ah in the same manner, meaning that Bakr bin Mudhar is not alone in narrating this hadith.
Imam Muslim has narrated the hadith of Layth with the following wording: When the Messenger of Allah sallallahu alayhi wa sallam performed prostration, he would keep his hands away from his armpits to such an extent that I could see the whiteness of his armpits.
(Sahih Muslim, Kitab al-Salat, Hadith: 1106 (495))

Hadith Commentary:
➊
Imam Bukhari rahimahullah, in this chapter, is further clarifying the completion of prostration (sujud) by stating that during prostration, the hands should be spread out and kept separate from the sides.
The Messenger of Allah sallallahu alayhi wa sallam used to perform prostration in this manner.
Moreover, during prostration, he would keep his elbows away from his sides.
The reason for this could be that during prostration, all parts of the body are engaged in prostration. If the body is contracted and the limbs are joined together during prostration, then all the limbs will be compressed into the form of a single limb, and each limb will not independently participate in the prostration as required by the Shari‘ah.
Thus, it is mentioned in the hadith that when a servant performs prostration, seven parts of his body also prostrate along with him: the face, both palms, both knees, and both feet.
In another hadith, it is stated that just as the face prostrates, both hands also prostrate.
(Sunan Abi Dawud, Salah, Hadith: 891, 892)
This is the reason why spreading the forearms (iftirash dhira‘ayn) during prostration is prohibited.
And Allah knows best.
➋
Hazrat Buhainah radi Allahu anha is the name of the mother of Abdullah radi Allahu anhu, and Hazrat Malik radi Allahu anhu is the name of his (Abdullah’s) father.
Contrary to the usual custom, Abdullah radi Allahu anhu is attributed to both his mother and father, which is why tanween is read at the end of Malik, and in “Ibn Buhainah,” the alif of “Ibn” should be written, because in this context, “Ibn” is not an attribute of Malik radi Allahu anhu.
(‘Umdat al-Qari: 3/356)
➌
Imam Bukhari rahimahullah, at the end, has mentioned a suspended (mu‘allaq) narration, which Imam Muslim rahimahullah has narrated with a connected chain, whose wording is that the Messenger of Allah sallallahu alayhi wa sallam, when he performed prostration, would keep his hands away from his arms to the extent that I could see the whiteness of his armpits.
(Sahih Muslim, Salah, Hadith: 1106 (495))
The purpose of mentioning this suspended narration is that in the aforementioned hadith, the narrator named Bakr narrated from his teacher Ja‘far ibn Rabi‘ah with the wording “an” (from), while Layth explicitly stated “haddathana” (he narrated to us) from him. Also, in that narration, the word “prostration” (sujud) was not explicitly mentioned; rather, the words were “when he prayed” (idha salla), whereas in Layth’s narration, the explicit wording “when he prostrated” (idha sajada) is present.
It should be noted that Imam Bukhari rahimahullah himself has also transmitted the wording “when he prostrated” (idha sajada) in one narration.
(Sahih al-Bukhari, Manaqib, Hadith: 3546)

Hadith Commentary: Benefits and Issues: Malik is the father of Abdullah, and Buhaina is their mother.

1107. Commentary: The Prophet sallallahu alayhi wa sallam used to keep the hair of his armpits clean, therefore white skin would be visible, or what is meant could be the whiteness around the hair. And Allah knows best.

Lexical Explanation:
«فَرَّجَ» is the past tense form from the verb tafreej (bab taf‘eel). Its meaning is: to create distance, openness, and spaciousness between the two sides.

Benefit:
From this hadith, it becomes clear that while performing prostration (sujud), one should keep one’s arms so far apart from the thighs that even the inner part of the armpits becomes visible. Based on this hadith, Imam Tabari rahimahullah and others have said that the armpits of the Prophet sallallahu alayhi wa sallam were white, just like the other pure parts of his body, and not black. This is one of his unique characteristics, just like his other distinctions. Tabari has explicitly mentioned this characteristic in the chapter of al-Ahkam, in the section of al-Istisqa, that his armpits were not black like those of others, but rather white.

Hadith Narrator: (Sayyiduna Ibn Buhaynah radi Allahu anhu) His full name is Abdullah bin Malik bin Qushab (with a kasrah under the letter “qaf” and the “sheen” being sakin). Buhaynah (in the diminutive form) is the name of his mother. He became well-known by his mother’s name, otherwise his father’s name is Malik. He was among the early Muslims. He was very ascetic, spent his nights in worship, and fasted during the day. He was extremely disinterested in worldly matters. He passed away in the valley of Raym, located thirty miles from Madinah, between 54 and 58 AH.