A benefit from al-Usūl al-Thalāthah lesson (2017/10/11) at TROID:

According to the strongest position, “Iqraʾ” (read) was the first piece of revelation. The first verses revealed to the prophet (صلى الله عليه وسلم) were:

اقْرَأْ بِاسْمِ رَبِّكَ الَّذِي خَلَقَ
خَلَقَ الْإِنسَانَ مِنْ عَلَقٍ
اقْرَأْ وَرَبُّكَ الْأَكْرَمُ
الَّذِي عَلَّمَ بِالْقَلَمِ
عَلَّمَ الْإِنسَانَ مَا لَمْ يَعْلَمْ 

Read! In the name of your Lord who has created (all that exists).
He has created man from a clot.
Read! And your Lord is the Most Generous.
Who has taught (the writing) by the pen.
He has taught man that which he knew not.
[Al-ʿAlaq, 96:1-5]

This was the introduction to the beginning of revelation. When the angel came and held him (the Prophet (صلى الله عليه وسلم)) tightly and then let him go, holding him tightly again and letting him go – the angel did this three times, each time saying: Read! The Prophet (صلى الله عليه وسلم) would reply: I am not able to read! Then the third time, the angel recited the verses to him and the Prophet went to Khadījah (raḍi Allāhu ʿanhā)—who was his pious, trusted, noble wife—and he informed her of that which occurred whilst trembling and frightened due to his unfamiliarity with that which had taken place.

Source: إتحاف العقول ص.١١٣
Translated by: Munīb al-Ṣumālī