Sikhism originated in 15th century India and was founded by Guru Nanak. It believes in one God and rejects idol worship. The religion continues to be led by a succession of gurus, with the final guru designating the holy text, Guru Granth Sahib, as his successor. Sikhism emphasizes equality and living a virtuous life according to its principles in order to achieve salvation. It is one of the largest organized religions in the world with over 25 million adherents.