Q-Does this appear in a Hadith?“When the Sahabah sat in gatherings of Nabi (sallallahu ‘alayhi wa sallam), if a sheet were to be spread over their heads it would not sag” i.e. they sat very close to each other.
Have not acome across any hadith states like this. The following narration is the closest I could locate although the context is different:
Sayyiduna Abu Tha’labah Al Khushani (radiyallahu ‘anhu) says, [When the Sahabah encamped after Jihad or enroute to Jihad] they would split up in the valleys and mountain passes.Rasulullah (sallallahu ‘alayhi wa sallam) said, ‘Your splitting up in the valleys and mountain passes is from Shaytan’.Thereafter whenever encamping, they would keep close to one another to such that it would be said ‘if a cloth were spread over them, it would cover them all.’(Sunan Abi Dawud, Hadith: 2621. Declared authentic by Imam Ibn Hibban; Al Ihsan, Hadith: 2690. Also see Hayatus Sahabah, vol. 1 pg. 768)
And Allah Ta’ala Knows best.
https://hadithanswers.com/how-did-sahabah-sit-in-gatherings/