It is famous that Ameerul Momineen (a.s.), Abu Bakr, Umar
and some other people sat on a carpet and by command of His
Eminence it soared and traveled to the people of the Cave.
Whoever of them greeted did not get any response, except Ameerul Momineen (a.s.) who greeted and received the reply.
The folks of the cave said:
“We don’t speak to anyone other than a prophet or a successor
of prophet.”
Behaarul Anwaar, vol. 39, p. 136
Isbaatul Wilayah (Part One) – Ayatullah AliNamazi Shahroodi (r.a.)