Muhammad didn’t know that he would be a Prophet: He led an ethical and ordinary life. He was known for his fidelity, integrity and trustworthiness. He never worshipped idols when idol worship was rife in a polytheistic society.
He always believed that the whole universe must have been created and controlled by one God. He used to worship God by retreating to a cave (634m above sea level) on a mount 4 km east of Mecca (Makkah).
The cave is known as Hira cave which is on a mount called "Jabal Al Noor" (i.e. Mount of light). This is because Muhammad received the first revelation from God when he was meditating in this cave.