SĀDHŪ SIṄGH, PAṆḌIT (1840-1907), a schoolman of the Nirmalā order, was born in the village of Saralīāṅ, in Amritsar district, in 1840. From his very childhood, he developed an inclination for the company of holy men. This was cause of concern for his father, Sobhā Siṅgh, and mother, Devī, who feared that their son might not renounce the world and become a recluse. Sādhū Siṅgh received instruction from a sant in his own village with whom he read the Sikh sacred texts. His thirst for knowledge eventually took him to the village of Girvaṛī, in the modern district of Hoshiārpur, where he joined the ḍerā or school of Paṇḍit Gulāb Siṅgh, a noted Nirmalā scholar of the day. Sādhū Siṅgh, then eighteen, resolved to give up the householder's life and dedicate himself to learning and to preaching the Sikh faith. In addition to Sikh theology, he studied Vedānta and Vyākarana (grammar). Long years of labour under Paṇḍit Gulāb Siṅgh made him an accomplished scholar and writer of Braj Bhāṣā.

        Paṇḍit Sādhū Siṅgh spent most of his years at Girvaṛī. For some time, he lived at Paṭiālā with another celebrated Nirmalā theologian, Paṇḍit Tārā Siṅgh Narotam, who had also been a pupil of Paṇḍit Gulāb Siṅgh. It is said that, at Paṭiālā, he became the successor of Paṇḍit Tārā Siṅgh after the latter's death in 1948 Bk/AD1891. He was also the Shrī Mahant, Abbot Senior, of the Nirmal Pañchāyatī Akhāṛā from 1905 till his death in 1907.

        Two of Paṇḍit Sādhū Siṅgh's works which have survived are Shrī Mukhvākya Sidhānt Jyotī and Guru Sikhyā Prabhākar. Both of these were lithographed in Chasmā-i-Nūr Press, Lahore, in 1950 Bk/AD 1893, in a single volume, under the title Guru Sikhyā Prabhākar. The volume has, in addition to the Vigyāpana notice or introduction, one small chapter containing eulogy of the Gurū Granth Sāhib and another in praise of Gurū as accepted in Sikh tradition and in praise of his teacher, Paṇḍit Gulāb Siṅgh. Then begins the first book Shrī Mukhvākya Sidhānt Jyotī, which contains 1,100 difficult and obscure words selected by the author from the Gurū Granth Sāhib with their meanings given in Punjabi, or Sādh Bhāṣā mixed with Punjabi. The vocables are arranged in alphabetical order of the first two letters of the words.

        Next comes the main book Guru Sikhyā Prabhākar, which, much larger in size, consists of five sections. The work, as the title indicates, deals with the teachings of the Sikh Gurūs. A verse from the Gurū Granth Sāhib or the Dasam Granth, containing some principle of Sikhism or a point of instruction, is set down or explained in detail, sometimes with further textual quotation. The format, in which the original verses are at places printed in separate lines in older letters and at others as part of the running text, is far from clear. Further, the language, highly stylized, is too difficult for an average reader.

        Part one of the book deals with subjects like the qualities of a gursikh (Sikh way of life), Divine will, and omniscience of God. In addition, moral values such as humility and selflessness are dilated upon, with appropriate quotation from the Gurū Granth Sāhib. Part two treats of metaphysical themes such as Brahman and ātman(ātmā, in Punjabi). There are additionally sub-sections on the qualities of a true yogī and the order of Khālsā. Part three is a large section, containing 212 sub-sections, each discussing a separate subject like Nām, various forms of bhaktī, grace and Advaita. Part four discusses the nature of Ultimate Reality according to Sikh thought. An important subject devoted to a whole section is the concept of haumai (self-centredness). The fifth part treats of subjects like sahaj (equipoise), sahaj samādhī (mystic trance, and contentment. An index of the subjects, dealt with in different sections, is given at the beginning. Paṇḍit Sādhū Siṅgh freely mixed verse with prose in his exposition. His poetry is in chaste Braj Bhāṣā, whereas his prose is mostly in Sādh Bhāṣā, overlaid with Sanskrit vocabulary.