Standardized by Committee in the Twentieth Century

Rehras Sahib's current fixed content, an assembled sequence of compositions by Guru Nanak, Guru Ramdas, Guru Arjan and Guru Gobind Singh, was not always uniform across the Sikh world, and its specific selection and length were formally standardized only in the twentieth century, through the Sikh Rehat Maryada, a code of conduct and practice developed by a representative committee and adopted in 1945 by the Shiromani Gurdwara Parbandhak Committee, the body overseeing major Sikh institutions including the Golden Temple, precisely in order to establish one agreed standard evening liturgy where regional and historical manuscript traditions had previously varied in exactly which compositions were included and in what order.

This institutional standardization effort was part of a broader twentieth century Sikh reform movement addressing considerable variation that had developed in liturgical practice, ritual custom and doctrinal interpretation across different Sikh communities and gurdwaras over preceding centuries, and the Rehat Maryada's fixing of Rehras Sahib's content is one concrete instance of that broader modern effort to establish a single agreed standard practice for the whole Sikh community rather than leaving significant liturgical variation between regions and lineages in place indefinitely. Older manuscripts and regional practice from before 1945 preserve evidence of that earlier variation, which specialists in Sikh liturgical history study to understand how the now standard evening prayer took its current settled form only relatively recently in the tradition's long history.