In his youth, Nanak began to compose hymns. At the age of 29, he had a mystical experience that led him to proclaim “There is no Hindu; there is no Muslim.” A strict monotheist, he rejected Hindu polytheism but accepted the Hindu concept of life as a cycle of birth, death, and rebirth; moksha, release from this cycle into unity with God, could be achieved only with the help of a guru, or spiritual teacher. Nanak believed that communion with God could be gained through devotional repetition of the divine name, singing of hymns and praises, and adherence to a demanding ethical code. He rejected idols and the Hindu caste system; it became a custom for Sikhs of all social ranks to take meals together. These beliefs are still central to modern Sikhism. Nanak was first in a line of ten gurus who shaped and inspired Sikhism. The fifth, Arjun (1563–1606), compiled hymns and other writings by earlier Sikh gurus, as well as medieval Hindu and Muslim saints, in the Adi Granth (First Book), or Guru Granth Sahib (the Granth Personified). This book became the sacred scripture of Sikhism. In addition to his spiritual leadership, Arjun wielded considerable secular power as he grappled with leaders of the Mughal Empire. The tenth guru, Gobind Singh (1666–1708), was both a scholar and a military hero. He established the Khalsa (community of pure ones), an order that combined spiritual devotion, personal discipline, and ideals of military valor. Baptism initiates new members into the Khalsa. The Adi Granth took its final form under the supervision of Gobind Singh, as did the Dasam Granth (Tenth Book), a collection of prayers, poetry, and narrative. After the deaths of his four sons, Gobind Singh declared the line of gurus at an end. The Adi Granth would instead be reverenced in houses of worship, taking the place of a living guru. Today, Sikhs worship at gurdwaras (temples), where the Adi Granth is the object of devotion. This book is consulted regarding questions of faith and practice. On certain occasions, it is recited in its entirety (requiring more than a day) or carried in procession; offerings may be placed before it. Worshipful singing, meditation, and focus on the divine name remain essential to spiritual life. Some Sikhs undertake pilgrimages to historical gurdwaras, such as the Golden Temple of Amritsar, that are associated with the gurus. Some become disciples of living saints. There is no established Sikh priesthood.