Sayyidah Aishah (may Allah be pleased with her) said: Revelation began for the Messenger of Allah (peace and blessings be upon him) with good dreams in sleep, and whatever dream he saw would come true in waking life like the light of dawn. Then solitude became dear to him, and he would stay alone in the Cave of Hira and worship there for many nights, before the longing to return home arose in his heart; and for this he would take provisions with him. Then (when the provisions ran out) he would again take the same amount of provisions from Sayyidah Khadijah (may Allah be pleased with her). Until, while he (peace and blessings be upon him) was in that Cave of Hira, revelation suddenly came to him (peace and blessings be upon him): the angel came to him (peace and blessings be upon him) and said: "Read!" He (peace and blessings be upon him) said: "I am not lettered." He (peace and blessings be upon him) said: Then Jibril (peace be upon him) took hold of me and pressed me so hard that I was left without strength. Then he released me and said: "Read!" I said: "I cannot read." Then he took hold of me and pressed me hard a second time, until I was exhausted. Then he released me and said: "Read!" I said: "(How shall I read?) I am not lettered." Then he took hold of me and squeezed me hard a third time, until my strength gave way. Then he released me and said: "Read in the name of your Lord who created (all things), who created man from a clot of blood. Read, and your Lord is the Most Generous, who taught by means of the pen" [Surah al-Alaq: 1-4]. He (peace and blessings be upon him) returned having heard these verses, his heart trembling (with fear), until he (peace and blessings be upon him) came to Sayyidah Khadijah (may Allah be pleased with her) and said: "Wrap me up, wrap me up." They wrapped him up until the fear left him. Then he (peace and blessings be upon him) said to Sayyidah Khadijah (may Allah be pleased with her): "O Khadijah! What has happened to me?" He told her the whole incident and said: "I fear for my life." Sayyidah Khadijah (may Allah be pleased with her) said to him (peace and blessings be upon him): "Never! Rejoice. By Allah! Allah Almighty will never disgrace you, for you (peace and blessings be upon him) maintain ties of kinship, speak the truth, carry the burden of the weak, earn for those who have no one to earn for them, honour your guests, and support the truth in calamities (and disputes)." Then Sayyidah Khadijah (may Allah be pleased with her) took him to Waraqah bin Nawfal bin Asad bin Abd al-Uzza bin Qusayy, who was Sayyidah Khadijah's paternal cousin. He had abandoned idol-worship and become a Christian in the time of Jahiliyyah; he used to write the Book in the Arabic language, and would write in Arabic as much of the Gospel as Allah willed him to write; and he had grown old and frail and become blind. Sayyidah Khadijah (may Allah be pleased with her) said to him: "O my uncle (cousin)! Listen to your nephew!" Waraqah bin Nawfal said: "O my nephew! (Tell me,) what have you seen?" He (peace and blessings be upon him) told him what he had seen, and Waraqah bin Nawfal said to him: "This is the same angel who was sent down to Musa (peace be upon him). Would that I were young at that time! Would that I were alive when your people will drive you out!" The Messenger of Allah (peace and blessings be upon him) said: "Will they drive me out?" Waraqah said: "Yes! (They will certainly drive you out.) Whenever any man has said the like of what you say, people became his enemies; and if I live to see your day, I will help you with all my strength."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17721