What was the beginning of Islam when the Prophet went to the cave and was unable to read?

The beginning of revelation to the Messenger of Allah, peace and blessings be upon him, was with truthful visions. Then, he was made to love seclusion in the cave of Hira for devotion. There, the angel Gabriel came to him and asked him to recite three times. Each time, the Prophet replied, "I am not a reciter," until the verses were revealed: ﴿Recite in the name of your Lord who created – Created man from a clinging substance. Recite, and your Lord is the Most Generous – Who taught by the pen﴾ up to His saying ﴿Taught man that which he knew not.﴾ The Prophet returned trembling to Khadijah, who reassured him that Allah would never disgrace him due to his praiseworthy qualities. Then, she accompanied him to Waraqah ibn Nawfal, who confirmed to him that this was the same angel (namus) who had descended upon Moses, and informed him that he would be expelled by his people. Then Waraqah passed away, and revelation ceased for a period. Afterwards, revelation continued with the descent of Surat Al-Muddaththir.