The very first revelation......

Assalamu alaikum warahmathullahi wabaraqathuhu!

We must have been reading the Qur'an for a long time, but how well do we know about the very first wahi (revelation); The Wahi that confirmed the prophethood of Muhammed (sal)?

When the prophet was in the 40th year of his life (i.e 40 years old) he began to go away from his house in the city of Makkah to a cave in the outskirts on top of a mountain called *Hira -(غار حراء Ġār Hirā-cave of Hira / aka Jabal Hira ). He used to take with him food and drink that was required for a few days, After it runs out, he used to come back home and stays for a while,then get more food and go back. This happened for a couple of months.
In the cave, he used to spend time meditating and praying to god in ways he saw fit. Not much is known about what exactly he did but the main idea was to cut off from the society, cleanse his heart and ponder over the purpose of life and worship of Allah.

Around the month of Rabi-ul-Awwal he started receiving another sign. His dreams became true. He would dream about certain incidents that would occur in the future as willed by Allah. This happened for 6 months. And in the month of Ramdhan in one of the odd nights in the last ten 10, he received his very first wahi. (i.e Laylathul Qadr -Night of decree)

He was in the cave meditating as usual when suddenly a strange figure that was emitting light appeared in front of him.The figure came close to him and squeezed him very tightly.Then released him and said إقرا- Iqra! Read!Then the prophet said مَا أَنَا بِقَارِئٍ - ma ane biqari. I do not know how to read! as the prophet was unlettered. Then the figure squeezed him harder and said إقرا the prophet  repeated مَا أَنَا بِقَارِئٍ for the second time. And for the 3rd time the figure squeezed the prophet, released him and said the following verses:

‏اقْرَأْ بِاسْمِ رَبِّكَ الَّذِي خَلَقَ - Read in the name of your Lord who created (all that exists)
 خَلَقَ الإِنْسَانَ مِنْ عَلَقٍ -Created man from a clot.
 اقْرَأْ وَرَبُّكَ الأَكْرَمُ‏‏ ‏-Read! And your Lord is most generous.

(Surah 96 : Al-Alaq)

Upon saying this the figure disappeared.The  prophet was very terrified and went to his house as fast as possible. He went to his wife Khadhija (RA) and said:      
 "‏"‏ زَمِّلُونِي زَمِّلُونِي Zammilooni, zammilooni- Cover me up! Cover me up! And he said : لَقَدْ خَشِيتُ عَلَى نَفْسِي-lakadh khasheethu ala naf'see- "I fear that something may happen to me"

On hearing this Khadhija (RA) replied:
"Never! By Allah, Allah will never disgrace you. You keep good relations with your kith and kin, help the poor and the destitute, serve your guests generously and assist the deserving calamity-afflicted ones."

(Note what a wise and understanding wife Khadhija (RA). May we all learn lessons from it in sha Allah.)

There upon Khadhija (RA) suggested that they go to her cousin Waraqa bin Nawfal who was a very wise man. He was one of the 4 who was searching for the true religion of Ibrahim (A)  . He had accepted Christianity and lived a pious life. He had become very old and was blind. When the prophet narrated the story he became overjoyed as he recognized Muhammed (sal) as the last prophet from the knowledge he gained from the previous scriptures.He said that the figure was "The one who keeps secrets" i.e Angel jibreel, who Allah had sent to Musa (A).  And he also added that he wished that he was young so that he could help the prophet when his people fight against him.

NOTE: Since Waraqa accepted Muhammed(Sal)'s prophethood first  he is considered the first muslim. While Abu Bakar (RA) is the first person who accepted islam upon prophet's invitation.

The prophet asked, "Will they drive me out?"  Then  Waraqa informed that anyone who had ever come with the same message i.e There is no god but Allah has been treated harshly. Further Waraqa added that if he stayed alive till that day he will support the prophet strongly. However after a few days Waraqa died and even wahi stopped for a while.

And then سورة المدثر - surah Mudassir was revealed. Starting with the ayah:

                                           
 يَا أَيُّهَا الْمُدَّثِّرُ
( Oh you who covers himself (in a garment     

NOTE : * Cave Hira is also called as Mountain of light (Jabal Noor) because of the significance of the revelation that occurred in it.

Reference to the revelation can be found in:
Sahih Bukhari, Volume 1, Book of revelation, Hadith no : 3