The claim
Revelation began in the cave of Hira nearly forty lunar years before the Hijra.
The evidence
-
The chain of transmitters — passage/muwatta-1-016
A Muwatta hadith with its isnad.
-
chronicle — event/first-revelation
The record of the first revelation — the night of power in the cave of Hira.
-
object — place/mecca
Mecca and its surroundings — where revelation began.
The historians' note
The sirah works agree revelation began in Hira; accounts differ on the day and month.