Sahib Singh was born Natthu Ram at Fatehjang in Attock district in 1892, in a Hindu family, and became a Sikh as a student.
He produced the first systematic grammar of the language of the Guru Granth Sahib Ji, the Gurbani Vyakaran, published in 1932. Before it, interpretation of the scripture rested on tradition and on the interpreter's judgement; after it, there was a grammatical basis for saying what a line meant.
The grammar showed that the endings on nouns and verbs in the text carry meaning consistently, which had not been recognised, and it changed the translation of a large number of passages.
His ten-volume commentary, the Sri Guru Granth Sahib Darpan, applies the grammar to the whole volume and remains the standard Punjabi commentary.
He also wrote on Sikh history and on the compilation of the scripture. Almost every serious reading of the Guru Granth Sahib Ji since 1932 rests on work done by a schoolteacher from Sialkot district.
He wrote it in Punjabi and it has to be read in Punjabi. There is no complete translation of the Darpan into any other language, which means the standard scholarly reading of the Guru Granth Sahib Ji is available only to somebody who reads Gurmukhi.
He taught at Khalsa College Amritsar and later at Gurmat College Patiala, and the work was done in the evenings of a teaching career. He had no research post, no funding, no assistant and no institution behind him.
The scale of it is the thing. A line by line reading of 1,430 pages with a grammar applied to every one of them, written by the time he was sixty-nine and published in ten volumes between 1962 and 1964, is the largest single piece of Punjabi scholarship of the twentieth century and one man did all of it.