It is narrated from Imam Hasan al-Askari(a.s)
that when the Prophet(s.a.w.a) reached the age of 40 years, the Almighty Allah made him, absolutely humble and sincere and found him to be the most obedient to Him. So He created a light in his eyes and when He issued the command, the doors of the heavens were opened up.
Angels arrived in groups to the earth to see the Prophet and the Almighty Allah joined His mercy from the leg of the Arsh to his eminence(s.a.w.a). Jibrael(a.s) came down encompassing the earth and the sky and holding the arm of the Prophet, he(a.s) said,
” Oh Muhammad, read.”
He(s.a.w.a) asked, ” What should I read?”
“Read in the name of your Lord who created. He created man from a clot. (Surah Alaq Verse 1)“
Then he conveyed divine revelation(wahy) to him.
According to another tradition, Jibrael(a.s) descended again, attended by 70,000 angels and Mikaeel by the same number and they brought a majestic throne for the Prophet, they placed the crown of prophecy, gave the banner of praise(لواء الحمد) in his hand and directed him to ascend the throne and praise the Lord.
According to another report, that throne was made of Ruby and its feet of Emeralds and pearls. When the angels returned to heaven, the Prophet descended from Mount Hira and such glory beamed from him that no one could endure the light. Every tree and herb and stone he passed, bowed down before his eminence and saluted him with the title of Messenger of Allah, saying in fluent language :
” Peace be on you, O Prophet of Allah.
Peace be on you, O Messenger of Allah.”
Reference: Hayatul Quloob V. 2, Chapter 24