The Nirmala order is the learned strand of the Sikh tradition, and its subject is exegesis rather than either arms or asceticism.
By tradition, Guru Gobind Singh sent a small group of Sikhs to Varanasi to study Sanskrit and the classical philosophical literature of India, so that Sikh scripture could be expounded with the technical apparatus that Brahminical learning possessed and the young tradition did not. They returned as Nirmalas, the spotless, and the traditional dating is around 1686. Scholars note that the order is scarcely mentioned in Sikh writing before the nineteenth century, and place its emergence in the early eighteenth.
Nirmalas are typically celibate, wear ochre, and do not ordinarily take Khalsa initiation. Their work was teaching. They established schools and centres, produced commentaries on the Guru Granth Sahib, translated Sanskrit texts into Punjabi and Braj, and supplied much of the theological literature the tradition had before the modern period. Their organisational centre, the Panchayati Akhara Nirmal, was established at Patiala in 1862 and now sits at Haridwar.
Their interpretive framework is Vedanta. They read Sikh scripture as teaching what the Upanishads teach, in a different idiom, and they treated the Indian philosophical inheritance as available material rather than as foreign matter.
The name is usually explained as meaning without stain. The order took it to describe a mind cleared for study rather than a body kept from the world, though its members generally maintained both.