Bukhari

Hadith Commentary:
It is understood from this that slaughtering a camel by making it stand and then performing nahr (slaughtering by piercing the throat at the base of the neck) is superior, and the Hanafis have considered both standing and sitting positions for nahr to be equal. However, this hadith refutes their view, because if it were so, Ibn Umar (radi Allahu anhu) would not have objected to that person. The name of that person is not known.
(Wahidi)
Hafiz Ibn Hajar (rahimahullah) states:
And in it is that the statement of a Companion, “This is Sunnah,” is considered marfu‘ (attributed to the Prophet sallallahu alayhi wa sallam) according to the two Shaykhs (Bukhari and Muslim), because they have used this hadith as evidence in their Sahih collections.
(Fath)
That is, it is also established from this hadith that when a Companion says regarding an action that “this is Sunnah,” then according to the two Shaykhs, it holds the status of a marfu‘ hadith, because the two Shaykhs have taken it as proof in their most authentic books, Bukhari and Muslim.

Hadith Commentary:
(1)
In Sunan Abu Dawud, it is narrated from Jabir radi Allahu anhu that when the Messenger of Allah sallallahu alayhi wa sallam and his noble Companions radi Allahu anhum would slaughter a sacrificial camel, they would tie its left leg and perform the nahr (slaughter) while it was standing.
(Sunan Abi Dawud, Al-Manasik, Hadith: 1767)
Sa'id ibn Jubayr states that he saw Ibn Umar radi Allahu anhu, and when he would perform nahr of a sacrificial camel, he would tie one of its legs.
From this, it is understood that tying one leg of the camel and performing nahr while it is standing is a virtue, although performing nahr while it is seated is also permissible. However, according to the Hanafis, there is equal virtue in performing nahr of the camel whether it is standing or seated.
(2)
The narration of Shu'bah has been transmitted by Ishaq ibn Rahwayh in his Musnad with a connected chain, whose wording is similar to the aforementioned narration.
(3)
From this hadith, it is understood that when a Companion uses the words "min as-sunnah" (from the Sunnah), it holds the status of a marfu' (elevated) hadith.
(Fath al-Bari: 3/699)

1768. Commentary: Complete adherence to the commands and actions of the Messenger (sallallahu alayhi wa sallam) is what constitutes true religion. The biographies of the noble Companions (radi Allahu anhum) demonstrate this very fact. They were always advocates of this, and this is the unalterable principle until the Day of Judgment. In the presence of explicit texts, what value do opinion, conjecture, inclination, and legal verdict hold!?