Before Islam and Hinduism spread to the areas surrounding the Saudi Arabian peninsula and India, there existed a large civilization called the Harappan. The Harappan had great cities, streets, homes situated in grid-like patterns, and large public buildings used for religious or government functions. What is remarkable is Harappan's had weights and measure standards, underground sewage systems, and they were at their peak of prosperity around 2500 B.C., well before Islam or Hinduism existed.
Harappan Civilization declined around 1500 B.C. only to be over taken by Aryan migrations. The Aryans came from northwestern Asia and settled in India, and spread their religion called Brahmanism, which worshipped many deities. Hinduism formed from Brahmanism and established a supreme and universal God, along with the many other deities. Hinduism believed in reincarnation, karma, and connecting with God by following one's individual path.
In a verse from one of Hindu's sacred text, the Bhagavad Gita, it states, "If you die in battle you will enter heaven..." The verse is directed toward a warrior since Hinduism is a caste system and the warrior is held in high regard as a priest and scholar.
Ironically, 2000 years later, Muhammad founded Islam around the same region, and in his holy text, the Qur'an, there is a verse about dying in battle, "Let those fight in the way of Allah who sell the life of this world for the other. Whoso fighteth in the way of Allah, be he slain or be he victorious, on him. We shall bestow a vast reward." (4:74) Obviously, Muhammad's version is more colorful than the Hinhu version, but it's difficult to get around the assumption that Muhammad may have been inspired by more than just the almighty Allah, a copy of the Bhagavad Gita would have been inspiring enough.