'Abdullāh ibn Yūsuf narrated to us; al-Layth narrated to us; 'Uqayl narrated to me; from Ibn Shihāb, who said:
I heard 'Urwah say that 'Āʾishah (may Allāh be pleased with her) said: The Prophet returned to Khadījah with his heart trembling. She took him to Waraqah ibn Nawfal, who was a man who had become a Christian and used to read al-Injīl (the Gospel) in Arabic. Waraqah said, “What do you see?” So, the Prophet ﷺ informed him. Waraqah said: “This is the Nāmūs (the bearer of the secret revelation) that Allāh sent down upon Mūsā. If I should live until the day when your people drive you out, I will support you with a strong support.”
“Nāmūs” means the keeper of the secret—the one who conveys to him what is hidden from others.
Reference: Sahih Al Bukhari 3392