When he was about 25 years old , his uncle suggested to him to work with the caravan which belonged to a wealthy widow named Khadijah . He accepted and undertook the journey to Syria . He conducted business with such prudence and sense of duty that he returned with larger profit than usual . Khadijah was so impressed by the honest and attractive personality of Muhammad that she offered to marry him which Muhammad accepted . This marriage was a happy one . They had children and most of them died in infancy . Khadijah was his only wife until she died when she was about 51 years old . Muhammad was born in the midst of Polytheistic ( unbellevers ) society. He was saddened and sick of the corrupt society around him . He often went to Hira cave in the mountain near Makkah , later known as Jabal An - Nur ( the mountain of Light ) where he meditated and pondered over the prevailing darkness of ignorance . Here he often remained deep in thought in communion with the unseen yet all - pervading God of the Universe . One night , while he was meditating in the Hira 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 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 . He was about 40 old at that time . The revelation continued to come to him from time to time in a period of 23 years . years These series of revelation were arranged according to the guidance given to the Prophet Muhammad ( peace be upon him ) and collected in the form of 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 verse , and some others were interpreted by the Prophet 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 God . People who follow this guidance and way of life are guaranteed by Allah to be saved in this world and the hereafter .