Abu Dawud

1037. Commentary:
In the final sentences of the Imam, it is correct that in the case of forgetting the middle sitting (qu‘dah), the prostration of forgetfulness (sajdah sahw) becomes obligatory. However, regarding whether it should be performed after the salutation (salam), the practice of the Companions (radi Allahu anhum ajma‘in) is varied: from some it is narrated before the salam, and from some after the salam [عون المبعود]
The preferred and superior opinion is that it should be performed before the salam.

1036. Commentary:
Shaykh al-Albani rahimahullah considers this hadith to be authentic, whereas other general hadith scholars deem it weak due to Jabir radi Allahu anhu. Because of his Rafidi beliefs, it is not acceptable as evidence. [عون المبعود۔ منذري]
However, the issue mentioned in it is established by the next hadith. The Shafi'is and others hold the view that reciting the tashahhud is obligatory; if the imam, or likewise someone praying alone, remains seated silently and does not recite the tashahhud, then upon remembering—before standing up straight—he should return to the sitting position and recite the tashahhud. This is the correct view. And if he stands up straight, then he should remain standing, and at the end, before the salam, perform two prostrations (sujood as-sahw).

Benefits and Issues:
➊
The mentioned narration has been declared weak in its chain by our esteemed researcher.
However, this narration is correct in both meaning and text.
Because regarding the issue mentioned in the hadith, in the investigation of Abu Dawood’s narration (1036),
our researcher writes that this narration is also weak in its chain.
But the upcoming narration (1037)
is sufficient in this regard.
Therefore, it is clear that the issue stated in the mentioned narration is also correct and sound according to our researcher.
The mentioned narration is only weak in its chain.
See: (Sunan Abu Dawood (Urdu)
Hadith 1036, published by Darussalam)
Allamah Shaykh al-Albani rahimahullah has declared it authentic.
See: (al-Sahihah no. 321)
Also, the researchers of Musnad Ahmad have declared it authentic as well.
For details, see: (al-Mawsu‘ah al-Hadithiyyah, Musnad al-Imam Ahmad: 162, 161, 101, 100/30)

➋
From this it is clear that if extra units (rak‘ahs) are started by mistake,
then they should be completed.

➌
If an extra rak‘ah is performed out of forgetfulness, then performing the prostration of forgetfulness (sajdat al-sahw) is sufficient.

Takhrij:
«أخرجه أبوداود، الصلاة، باب من نسي أن يتشهد وهو جالس، حديث:1036، وابن ماجه إقامة الصلوات، حديث:1208، والدارقطني:1 /379، وللحديث شاهد بمتن آخر عند الطحاوي في معاني الآثار (1 /440)، وسنده حسن، وانظر نيل المقصود:1037 فهو يغني عنه.»©Explanation:
The aforementioned narration has been declared severely weak in its chain by our esteemed researcher, hafizahullah, and he has further written that there is a corroborating narration (shahid) which Imam Tahawi has mentioned in Ma‘ani al-Athar, and its chain is hasan (good). He has also written that the hadith of Sunan Abi Dawud (1037) suffices for this issue. Therefore, it is understood that if a person praying forgets to sit for the middle tashahhud, and if he has not yet fully stood up but is still closer to the sitting position, then he should sit down and recite the tashahhud; this is the correct view. However, if he has already stood up straight, then he should remain standing and perform two prostrations (sujood as-sahw) before the final salam.