Bukhari

Hadith Commentary: Qastallani (rahimahullah) said: It is clearly understood from this that i‘tidal, that is, standing up straight after bowing (ruku‘), is a lengthy pillar (rukn) of the prayer. The statement of those who have denied this is invalid and unworthy of attention.

Hadith Commentary:
(1)
There is brevity in this narration.
Imam Bukhari rahimahullah has mentioned it in detail under the chapter "The Pause Between the Two Prostrations." Thus, Thabit says that Anas radi Allahu anhu used to perform such actions during prayer that I have not seen you people doing.
When he would raise his head from bowing (ruku‘), he would stand for such a long time that someone might say:
Perhaps you have forgotten.
(Sahih al-Bukhari, al-Adhan, Hadith: 821) (2)
From this narration, it is understood that in the time of Thabit, people did not prolong the standing (qawmah) after bowing or the sitting between the two prostrations, whereas Anas radi Allahu anhu would prolong them to such an extent that an onlooker would think perhaps he had forgotten.
(3)
The commentators have mentioned several meanings for "forgetting," for example:
٭ He forgot to perform the prostration.
٭ He forgot that perhaps he is not standing in prayer.
٭ He mistakenly thought that perhaps it is the time for qunut.
(Fath al-Bari: 2/373)

Hadith Commentary:
Vocabulary of the Hadith:

DĀRĀT:
It is the plural of DĀRAH.
It refers to the sides and surroundings of the mouth,
meaning that the circumference of the face prostrates,
therefore, it will be protected from the Fire.