I have heard the following description regarding the donkey of Dajjal:
“The donkey will have a door on its belly and that people could go in and out of the donkey’s belly through that door.” (Biharul Anwar).
Is it authentic?
I have not come across this narration describing Dajjal’s donkey in any authentic primary source nor in any secondary source.
The source cited in the question is a Shi’i source. The narration should not be quoted.
See here for part of the description of Dajjal’s donkey in an authentic narration.
And Allah Ta’ala Knows best.
Answered by: Moulana Suhail Motala
Approved by: Moulana Muhammad Abasoomar