The religious weight of Gurmukhi comes from what is written in it. The Adi Granth, compiled by Guru Arjan in 1604 and expanded into the Guru Granth Sahib, is written in Gurmukhi throughout, even though its hymns are composed in several languages, including Punjabi, Braj, Persian and Sanskrit-derived idioms. The script is thus the single written body that holds a multilingual scripture together.
Because Sikhs revere the Guru Granth Sahib as the living Guru, the reverence extends to its letters: the volume is installed, attended, and ceremonially retired, and copying or printing it is governed by strict custom. Learning Gurmukhi has historically been an act of piety, taught in the gurdwara so that every Sikh can read the Guru's words without an intermediary, and the tradition remembers the early Sikh schools as instruments of this democratising purpose. Calligraphed folios of the scripture, and the ik onkar monogram that opens it, are the visual emblems of the faith. In the diaspora, Gurmukhi literacy classes remain a standard part of gurdwara life, because access to scripture in its own script is understood as part of the inheritance every Sikh should receive. The Dasam Granth and the compositions of Bhai Gurdas, the early expositor of Sikh teaching, travel in the same letters.