Sadhu Singh, 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 Vedanta and Vyakarana (grammar). Long years of labour under Pandit Gulab Singh made him an accomplished scholar and writer of Braj Bhasa. Pandit Sadhu Singh spent most of his years at Girvan.For some time, he lived at Patiala with another celebrated Nirmala theologian, Pandit Tara Singh Narotam, wlio had also been a pupil of Pandit Gulab Singh. It is said that, at Patiala, he became the successor of Pandit Tara Singh after the latter`s death in 1948 Bk/AD 1891.
He was also the Shri Mahant, Abbot Senior, of the Nirmal Pahchayati Akhara from 1905 till his death in 1907. Two of Pandit Sadhu Singh`s works which liave survived are Shn Mukhvakya Sidhant jyoti and Guru Sikhya Prabhakar.Both of these were lithographed in Chasmai-Nur Press, Lahore, in 1950 Bk/AU 1893, in a single volume, under the title Guru Sikhya Prabhakar. The volume has, in addition to the Vigyapana notice or introduction, one small chapter containing eulogy of the Guru Granth Sahib and another in praise of Guru as accepted in Sikh tradition and in praise of his teacher.
Pandit Gulab Singh. Then begins the first book Shn Mukhvakya Sidhant Jyoti, which contains 1,100 difficult and obscure words selected by the author from the Guru Granth Sahib with their meanings given in Punjabi, or Sadh Bhasa mixed with Punjabi. The vocables are arranged in alphabetical order of the first two letters of the words. Next comes the main book Guru Sikhya Prabhakar, which, much larger in size, consists of five sections. The work, as the title indicates, deals with the teachings of the Sikh Gurus.
A verse from the Guru Granth Sahib 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 Guru Granth Sahib. Part two treats of metaphysical themes such as Brahman and atman (atma, in Punjabi).There are additionally subsections on the qualities of a true yogi and the order of Khalsa. Part three is a large section, containing 212 subsections, each discussing a separate subject like Nam, various forms of bhakti, 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 haiunai (self centredness). The fifth part treats of subjects like sahaj (equipoise), sahaj samadhi (mystic trance, and contentment. An index of the subjects, dealt with in different sections, is given at the beginning. Pandit Sadhu Singh freely mixed verse with prose in his exposition. His poetry is in chaste Braj Bhasa, whereas his prose is mostly in Sadh Bhasa, overlaid with Sanskrit vocabulary.
1. Pritam Singh, Mahant, Nirmal Panth Darshan. Amritsar, 1953
2. Dial Singh, Mahant, Nirmal Panth Darshan. Amritsar, 1953
3. Ganesha Singh, Mahant, Nirmal Bhushan arthat Itihas Nirmal Bhekh. Amritsar, 1957