For the 25 million Sikhs across the globe, their holy book is the living Guru. The centrality of the Guru Granth Sahib (GGS) in the life of the Sikhs is a unique phenomenon in the history of religion. The primary devotional practice of the religion is kirtan, the singing of the scriptural hymns in the accompaniment of musical instruments. From rural Punjab to metropolitan centers around the world, Sikh celebrations include processions with colorful floats displaying the GGS. The GGS serves as the centripetal force that joins congregations across the world. It was through the sacred verse that "Sikh" subjectivity came into being, and through its melodious lyrics it is being sustained. The origins of the GGS are traced back to the founder of Sikhism, Guru Nanak. Guru Nanak's successors continued on his spiritual legacy. At the very outset Sikh scripture celebrates the singular ontological reality – Ikk Oan Kar – "One being is".