Nasai

Hadith Commentary:
Sitting briefly before standing up for the second or fourth rak‘ah is called the “jalsah al-istirahah” (session of rest). This is what is mentioned in this hadith.

Al-Hafiz said in Fath al-Bari: “In it is the legitimacy of the jalsah al-istirahah, and al-Shafi‘i rahimahullah and a group from among the people of hadith acted upon it.” That is, in Fath al-Bari, Hafiz Ibn Hajar stated that the legitimacy of the jalsah al-istirahah is established from this hadith, and Imam al-Shafi‘i rahimahullah and a group from among the Ahl al-Hadith have acted upon it.

However, the Hanafis have denied the jalsah al-istirahah. Thus, it is written in one place:
“This is the jalsah al-istirahah, and according to the Hanafis, it is better not to do so. In the beginning, this was the method, but later it was abandoned.” (Tafhim al-Bukhari, p. 81)

Further on, the same author himself refutes his own opinion. Thus, he states: “Here, it should also be kept in mind that the difference is only to the extent of superiority (afdaliyyah).” From this, it is clear that he considers it permissible (in the degree of permissibility). Then how correct is it to say that it was later abandoned? We do not wish to prolong this discussion. We will only quote the commentary of Mawlana Abdul Hayy Sahib Hanafi of Lucknow. He writes:

“Know that most of our Hanafi scholars and many of the Sufi shaykhs have mentioned, in the manner of performing Salat al-Tasbih, the method narrated by al-Tirmidhi and al-Hakim from Abdullah ibn al-Mubarak, which does not include the jalsah al-istirahah. Whereas the Shafi‘is and most of the hadith scholars have preferred the method that includes the jalsah al-istirahah. And it is clear from what we have previously stated that, in terms of authenticity, the correct way is that which includes the jalsah al-istirahah. Therefore, whoever performs it, whether Hanafi or Shafi‘i, should certainly perform the jalsah al-istirahah when praying Salat al-Tasbih.” (Tuhfat al-Ahwazi, p. 237, referencing Kitab al-Athar al-Marfu‘ah)

That is, know that most of our Hanafi scholars and Sufi shaykhs have mentioned Salat al-Tasbih in the manner narrated by al-Tirmidhi and al-Hakim from Abdullah ibn al-Mubarak, but in that narration, there is no mention of the jalsah al-istirahah. Whereas the Shafi‘is and most of the hadith scholars have preferred the method that includes the jalsah al-istirahah. And from our previous explanation, it is clear that, in terms of authenticity, the correct way is to perform the jalsah al-istirahah. Therefore, whether one is Hanafi or Shafi‘i, whenever he prays Salat al-Tasbih, he should certainly perform the jalsah al-istirahah.

The great hadith scholar, Allamah Abdur Rahman Mubarakpuri rahimahullah, states:
“The Hanafis and others who do not accept the jalsah al-istirahah have excused themselves from acting upon the hadith of Malik ibn al-Huwayrith radi Allahu anhu mentioned in this chapter with excuses, all of which are weak.” (Tuhfat al-Ahwazi)

That is, those who do not accept the jalsah al-istirahah, such as the Hanafis and others, have presented several excuses for not acting upon the hadith of Malik ibn al-Huwayrith radi Allahu anhu, which is mentioned here in al-Tirmidhi (and is also before the readers in Sahih al-Bukhari), but none of these excuses have any substance and should be considered baseless excuses.

(For further details, one should study Tuhfat al-Ahwazi.)

Hadith Commentary:
If, in order to teach people the prescribed (masnun) method, one performs prayer in front of them, then this will not be considered as performing it for other than Allah, nor can it be called ostentation (riya) for which there is a severe warning.

Similarly, when Malik bin Huwairith (radi Allahu anhu) said that he did not intend to pray, the purpose was not that he was not praying with the intention of reward, but rather he was explaining to them the reason for praying at that time: that I am praying with the intention of teaching and showing you, as is explicitly stated in another narration.
(Sahih al-Bukhari, al-Adhan, Hadith: 824)
(2)
Malik bin Huwairith (radi Allahu anhu) understood that teaching through action is more appropriate and beneficial than teaching through words, thus doing so is not "shirk in worship" but is exactly in accordance with the requirements of the Shari‘ah.
(Fath al-Bari: 2/212)
Furthermore, this hadith also proves the session of rest (jalsat al-istirahah), and by this is meant to sit briefly after rising from the prostration (sujud) of the first and third rak‘ah before standing up.
We will explain this in detail later,
insha’Allah.

842. Commentary:
Sitting briefly after the second prostration (sajdah) in the first and third units (rak‘ah) before standing up is customarily called the "jalsah of rest" (jalsah istirahah). This sitting is an act of worship (‘ibadah) and is Sunnah.