Abu Dawud

Takhrij al-Hadith:
[مسند احمد : 386/1، سنن ابي داود 995، سنن النسائي : 1177، سنن الترمذي : 366]

Commentary:
Its chain of narration is "mursal," and for this reason, it is "weak," because:
Abu Ubaydah did not hear from his father, Sayyiduna Abdullah ibn Mas'ud radi Allahu anhu.

◈ Hafiz Ibn Hajar rahimahullah writes:
The preferred opinion is that Abu Ubaydah did not hear from his noble father. [تقريب التهذيب : 8231]

◈ He also states:
"According to the majority of scholars, he did not hear from his noble father." [موافقة الخبر : 364/1]

Therefore, it is not correct for Imam Hakim rahimahullah [1/ 296] to declare this narration as 'authentic according to the conditions of Imam Bukhari and Muslim.'

◈ Regarding this narration, Hafiz Ibn Hajar rahimahullah says:
"This narration is disconnected (munqati‘), because Abu Ubaydah did not hear from his noble father." [اتلخيص الحبير : 263/1، ح : 406]

The second point is that this does not negate the recitation of salutations (durud) in the first tashahhud; rather, at most, it establishes that the first tashahhud was shorter than the second. That is, even with salutations (durud) included, the first tashahhud could still be shorter compared to the second.

◈ Allamah Shawkani rahimahullah (1250–1173 AH) writes:
"In this hadith, there is only the legislation of making the first tashahhud short, and that is achieved by making it shorter than the second tashahhud." [نيل الاوطار : 2/ 333]

995. Commentary:
Ibn Abi Shaybah has narrated with a sound chain from Tamim bin Salamah that the sitting posture of Abu Bakr radi Allahu anhu and Umar radi Allahu anhu was such that it was as if they were sitting on a hot stone. See: [التلخيص الجبير 263/1]
This indicates that after two rak‘ahs, reciting only the tashahhud is sufficient; however, if one also recites salutations upon the Prophet (salawat/darood sharif) after that, it is better. That is, reciting salutations upon the Prophet (salawat/darood sharif) in the first tashahhud is also recommended (mustahabb). For details, see: [صفة الصلاة النبى صلى الله عليه وسلم للباني ص 45]

1177. Commentary: This narration is weak; however, in Ibn Abi Shaybah, it is narrated with a sound chain from Tamim ibn Salamah that the manner in which Abu Bakr and Ibn Umar (radi Allahu anhuma) would sit in the first tashahhud was as if they were sitting on a hot stone. See: [التلخیص الجبیر : 263/1] From this, it is understood that after two rak‘ahs, merely reciting the tashahhud is sufficient. However, if one also recites salutations upon the Prophet (salat al-ibrahimiyyah, i.e., durood sharif) after that, it is better. That is, reciting durood sharif in the first tashahhud is also recommended (mustahabb), as has been mentioned previously. And Allah knows best. For further details, see: [صفة صلاة النبي صلی اللہ علیه وسلم للألباني ، ص : 45]

1:
That is, they would get up very quickly.

2:
That is, he said something quietly which I could not hear.

3:
This narration from Ibn Mas'ud (radi Allahu anhu) is weak in its chain of transmission,
but the narration reported from Abu Bakr (radi Allahu anhu) with the same meaning is authentic,
and the practice of the Ummah is based upon that.

Note:
(Abu Ubaydah did not hear directly from his father, Ibn Mas'ud (radi Allahu anhu))