It was
narrated that Harith bin Hassan said:
“I came to Al-Madinah
and saw
the Prophet (ﷺ) standing on the pulpit, and Bilal standing
in front
of him, with his sword by his side, and (I saw) a black flag.
I said:
‘Who is this?’ He said: ‘This is ‘Amr bin ‘As, who has just
come back from a campaign.’”