Bukhari

Hadith Commentary:
(1)
From this hadith, the intent of the Shariah is understood to be that every pillar of the prayer should be performed with complete calmness and tranquility, such that every limb of the body comes to rest in its proper place with composure and assurance. In the view of the Shariah, prolonged standing (qiyam) does not hold as much importance, because the duration of standing can vary according to circumstances and conditions. However, regarding the four positions—namely, bowing (ruku‘), standing after bowing (qawmah), prostration (sujud), and the sitting between the two prostrations—the practice of the Messenger of Allah (sallallahu alayhi wa sallam) always remained consistent.
(2)
It should be noted that the shaykh mentioned in the hadith refers to ‘Amr ibn Salamah al-Jarami (radi Allahu anhu). (: Fath al-Bari: 2/375)
This hadith also mentions the sitting of rest (jalsat al-istirahah), the explanation of which we will provide under hadith: 823.

Folding the Hands in Qiyam after Ruku

Whether or not the hands should be folded in qiyam (standing) after ruku, there is nothing explicitly established on this issue. Therefore, both practices are permissible, but it is better that the hands are not folded in qiyam after ruku.

Imam Ahmad ibn Hanbal rahimahullah was asked: Should the hands be folded after ruku or left hanging? He replied: «أرجو أن لا يضيق ذلك إن شاء الله» [مسائل احمد رواية صالح بن احمد بن حنبل: 615]

“I hope, insha Allah, there is no restriction in this matter.”

Hadith Commentary:

After the odd-numbered units (rak‘at), that is, after rising from the second prostration (sajdah) of the first and third rak‘at, to sit briefly and then stand up—this is called the "jalsah istirahah" (sitting of rest), which is established from authentic Sunnah.

Hadith Commentary:
(1)
The legitimacy of the sitting of rest (jalsat al-istirahah) is established from this hadith, the manner of which is described in one narration with these words: The Messenger of Allah (sallallahu alayhi wa sallam), while saying “Allahu Akbar” (Allah is the Greatest), would rise (from the second prostration), fold his left foot and sit upon it, then stand up (for the second rak‘ah).
(Sunan Abi Dawud, Kitab al-Salat, Hadith: 730)

(2)
When rising from the sitting of rest, both hands should be placed on the ground for support, as clarified in the next hadith.

(3)
Some scholars declare the sitting of rest to be obligatory because the Messenger of Allah (sallallahu alayhi wa sallam) commanded the one who prayed incorrectly (musi’ al-salat) to do so, as mentioned in the hadith.
(Sahih al-Bukhari, Kitab al-Isti’dhan, Hadith: 6251)
After teaching the actions of prayer to the narrator of the aforementioned hadith, Malik ibn al-Huwayrith (radi Allahu anhu), the Prophet (sallallahu alayhi wa sallam) finally said: “Pray as you have seen me praying.”
(Sahih al-Bukhari, Kitab al-Adhan, Hadith: 631)

(4)
Imam al-Tirmidhi (rahimahullah) has established a separate chapter to explain the method of rising after the second prostration. For this, he mentioned the aforementioned hadith from Malik ibn al-Huwayrith (radi Allahu anhu) as found in Sahih al-Bukhari, then stated that this is the practice of some people of knowledge, Imam Ishaq ibn Rahwayh, and our companions.
(Jami‘ al-Tirmidhi, Kitab al-Salat, Hadith: 287)
Then Imam al-Tirmidhi (rahimahullah) established another chapter and narrated the hadith of Abu Hurayrah (radi Allahu anhu), in which it is mentioned that the Messenger of Allah (sallallahu alayhi wa sallam), after completing the second prostration, would stand up on the balls of his feet without sitting for the sitting of rest, and he wrote that some people of knowledge also act upon this. However, regarding this hadith, he stated that there is a narrator, Khalid ibn Iyas, who is considered weak among the hadith scholars.
(Jami‘ al-Tirmidhi, Kitab al-Salat, Hadith: 288)
Al-‘Allamah al-Albani (rahimahullah) has also declared this hadith to be weak.
(Irwa’ al-Ghalil, Hadith: 362)

(5)
Some scholars differ regarding the sitting of rest. They say that if it had been the constant practice of the Messenger of Allah (sallallahu alayhi wa sallam) to perform the sitting of rest, then everyone who described the method of prayer would have mentioned it. The answer to this has been given by Hafiz Ibn Hajar (rahimahullah) in these words: Not every unanimously agreed-upon Sunnah has been completely described by every narrator; rather, the totality of them has been taken from the Companions (radi Allahu anhum), so this objection holds no weight.
(Fath al-Bari: 2/391)
It is generally observed that after rising from the prostration of recitation (sajdat al-tilawah) in prayer, the imam and the followers do not sit for the sitting of rest, but rather stand up directly for the standing position, even though the generality of the hadiths on this issue indicate that the sitting of rest should also be performed after the prostration of recitation.
And Allah knows best.

(6)
The opponents of the sitting of rest also present some reports from the Companions (radi Allahu anhum), but these have no standing in comparison to the marfu‘ (Prophetic) hadiths.
And Allah knows best.

(7)
There is no evidence that the Messenger of Allah (sallallahu alayhi wa sallam) performed the sitting of rest due to weakness or illness. Likewise, the analogy that the subject of prayer is not rest is also invalid. This analogy is rejected because it is in opposition to the textual evidence.

1:
This sitting is called Jalsat al-Istirahah (the sitting of rest).
This hadith indicates the legitimacy of Jalsat al-Istirahah.
Those who do not accept the Sunnah status of Jalsat al-Istirahah have made various interpretations of this hadith,
but these are interpretations that are absolutely unworthy of consideration.
Furthermore, the hadith regarding standing up without the support of the feet is weak, which will be mentioned ahead.

844. Commentary:
➊ These hadiths establish that the sitting of rest (jalsah al-istirahah) in the first and third units (rak‘ah) is a Sunnah and recommended (mustahabb) act.
➋ The noble Companions (radi Allahu anhum ajma‘in) were extremely diligent, especially regarding the congregational prayer. They preserved even its minute details and conveyed them to the Ummah.

1154. Commentary:

➊ It has already been mentioned in Hadith number 1092 that the hands serve as support for a person, and standing up or sitting down without the support of the hands resembles the way of camels or, in fact, ordinary animals, which is not appropriate. In one narration of Sunan Abu Dawood, support (with the hands) has been prohibited. Hafiz Ibn Hajar rahimahullah has declared it weak. Shaykh al-Albani rahimahullah has declared it munkar. See, [ضعیف سنن ابن داود ، رقم : 992]

➋ Consequently, it is also understood that when rising, the knees should be lifted first and the hands afterwards, because the support is removed last, and this is easier. Elderly people will also be able to stand up easily in this way.

1153. Commentary: Sitting straight before standing for the next rak‘ah after an odd-numbered rak‘ah is called the “jalsah al-istirahah” (resting sitting), and this is necessary. In addition to this hadith, there are several other ahadith in which this is explicitly mentioned, both in words and in action. Some individuals who do not accept this attribute it to the old age of the Prophet sallallahu alayhi wa sallam, claiming that due to old age he had to sit, and that it was not a Sunnah of the prayer. However, they have no evidence for this interpretation, whereas the noble Companions radi Allahu anhum, who witnessed it with their own eyes, did not understand it to be due to old age. This is evident from the fact that when Abu Humayd radi Allahu anhu mentioned this matter in the description of the Prophet’s sallallahu alayhi wa sallam prayer before ten Companions, and those Companions remained silent, it is a clear proof. The verbal narration regarding the one who prayed incorrectly (hadith of al-musi’ fi salatihi) is also explicit. If this is not mentioned in some narrations, it is due to brevity. The ruling on any matter should be derived from the collective body of ahadith; therefore, the absence of its mention in a hadith does not negate its obligation. The understanding of the noble Companions radi Allahu anhum is certainly more reliable than that of those who came after. Moreover, the Prophet sallallahu alayhi wa sallam, even in old age, did not become so weak that he would have to abandon or change an established religious matter.

Lexical Explanation:
«فِي وِتْرٍ مِنْ صَلَاتِهِ» When you completed an odd rak‘ah, that is, the first or third rak‘ah, and wished to stand for the second or fourth,
«لَمْ يَنْهَضْ» you would not stand up immediately.
«حَتَّى يَسْتَوِيَ قَاعِدًا» Rather, you would first sit upright and completely, and only then stand up. This is called the “sitting of rest” (jalsat al-istirahah), and it is Sunnah and legislated.

Benefit:
The legitimacy of the sitting of rest (jalsat al-istirahah) is established from this hadith. Imam al-Shafi‘i rahimahullah holds this view, but Imam Ahmad and Imam Abu Hanifah rahimahumallah do not. They interpret it as being due to old age. However, this interpretation is not correct. The Prophet sallallahu alayhi wa sallam said to Sayyiduna Malik radi Allahu anhu and his companions: «صَلُّوا كَمَا رَأَيْتُمُنِي أُصَلِّي» “Pray as you have seen me praying.” [صحيح البخاري، الصلاة، حديث : 631] And he (Malik) himself narrates that you (the Prophet) used to perform the sitting of rest. When the very narrator of the hadith did not interpret it as being due to old age, then to do so is mere arbitrary assertion.