Hymn qualities of God and why one should meditate on God's name. The "Guru Granth Sahib" is divided by their musical setting in different ragas into fourteen hundred and thirty pages known as "Angs" (limbs) in Sikh tradition. Guru Gobind Singh (1666–1708), the tenth guru, after adding Guru Tegh Bahadur's bani to the Adi Granth affirmed the sacred text as his successor, elevating it to "Guru Granth Sahib". The text remains the holy scripture of the Sikhs, regarded as the teachings of the Ten Gurus. The role of Guru Granth Sahib, as a source or guide of prayer, is pivotal in
Adi Shankara ("Bhāṣya"), original philosophical expositions ("Prakaraṇa grantha") and poetry ("Stotra"). However most of these are not authentic works of Adi Shankara and are likely to be works of his admirers or scholars whose name was also Shankaracharya. Piantelli has published a complete list of works attributed to Adi Sankara, along with issues of authenticity for most. Adi Shankara is most known for his systematic reviews and commentaries ("Bhasyas") on ancient Indian texts. Shankara's masterpiece of commentary is the "Brahmasutrabhasya" (literally, commentary on Brahma Sutra), a fundamental text of the Vedanta school of Hinduism. His commentaries on ten Mukhya (principal) Upanishads are