One night, while he was meditating in the Hera cave, the Angel Gabriel came to him. The Angel aroused him and his mighty voice reverberated in his ears. He was perplexed and did not know what to do. He was asked to read" He replied: "I cannot read!" The Angel repeated three times asking Muhammad Sallallahu Alayhi Wasallam to read. He replied the same answer. Finally the Angel said:
"Read In the name of your Lord, who created man from a clot. Read in the name of your God, the Most Bountiful, who taught by means of the pen, and taught man what he did not know.”
This was the first revelation received by Muhammad Sallallahu Alayhi Wasallam. He was about 40 years old at that time. The revelation continued to come to him from time to time in a period of 23 years.
These series of revelation were arranged according to the guidance given to the Prophet Muhammad Sallallahu Alayhi Wasallam and collected in the form of a book called Al-Mushaf which was also called Qur'an (Reading). Most of its verses have the clear meaning. Some verses are interpreted in conjunction with other verses) and some others were interpreted by the Prophet Sallallahu Alayhi Wasallam himself through his words, actions and agreements which are famously known as his Sunnah (Traditions).
The Quran and the Sunnah combined together constitute the guidance and way of life for those who submit their life to Allah. People who follow this guidance and way of life are guaranteed by Allah to be saved in this world and the hereafter.