Because it is the first sign that he is a prophet and that he is gods messenger
The Holy Prophet(p.b.u.h) received his first revelation in the month of Ramadhan.
The first verses of Sura Alaq were revealed to the holy Prophet-saw. The Qur'an was the first written text of Islam.
Hazrat ADAM (AS) was the first holy Prophet.
Islam's Most important religion figure is Prophet Muhammad (peace be upon him). Prophet Muhammad is God messenger and prophet who received God revelation of Quran, Islam religion holy book, through the angel Gabriel (Jibril).
The holy book of Islam is Quran that reflects real God revelation to prophet Muhammad; peace be upon him; through the angel Jibril (or Gabriel). Besides the Quran, there is the Prophet Hadith (prophet sayings and practices)
On the Ninth of Dhu al-Hijjah, 10 A.H. (632 CE)
No Muslim figure is holy per Islam teachings. However, prophet Muhammad is the prophet of Islam religion per God Quran revelation to him through the angel Gabriel (Jibril)
It was the prophet Jeremiah.
Quran is the holy book of Islam per prophet Muhammad (peace be upon him). It is holy because it reflects real Allah (or God and same God in Christianity and Judaism) words revelation to prophet Muhammad through the angel Gabriel (or Jibril).
There were many writers of the Wahee (revelation). Hazrat Amir Muawia (RA) was one of them.
The question isn't quite clear, but from what i gathered you mean the revelation sent to the Prophet (pbuh)? The angel Jibreel (as) came down from the heavens as a command from Allah (swt) and revealed the first verse of the Qur'an to him. Hope that answers it :)
Any Muslim has the Quran (or Koran) as his holy book that reflects real God words revelation to Prophet (PBUH).