ਮੰਗਲਾਚਰਨ
Why did the Singhs learn Sanskrit - Giani Gian Singh

[The following is from Giani Gian Singh's Twarikh Guru Khalsa, written in 1880CE]
One day a thought arose to Guru Gobind Singh; “My Sikhs have learned Shastar Vidiya and remain ready to fight at all times [tyaar bar tyaar], but to get them out of the trappings of ritual action [karam kaand], the Puranas and idol worship, it would be necessary for them to study and have an understanding of the [ancient] Sanskrit [texts]. Because, otherwise they will be trapped in that mindset, without being able to use their pragmatic and progressive minds [with higher understandings of Vedant].”
With this thought in mind Guru Ji called on Pandit Raghnath Daas to teach his Sikhs Sanskrit. After a few days of instruction had passed, the Pandit had questioned the Sikhs as to their caste, some replied by saying they were carpenters, landowners, barbers, textile workers, etc, and the Pandit subsequently stopped the instruction. Even after the Guru Ji told him a second time to instruct his Sikhs the Pandit refused, replying to the Guru, “Your Sikhs are largely of low caste, who do not have the right to learn the wisdom of the Vedas. In the Dharam Shaastar [texts that ascribe codes of conduct] it states that those of low caste, and those who instruct the low caste, on the wisdom of the Vedas deserve to be spat in the mouth upon. It’s irrelevant that no Raja today will serve this punishment, my caste will still renounce me.” Listening to the Brahmans words, Guru Ji said, “Oh Brahman, those Sikhs who you are calling low caste, you Brahmins will be learning Sanskrit from those Sikhs in the future, they will be your Guru. Your ego will be taken away by the Highest Lord, [the Guru then recited]"
ਅਹੰਕਾਰੀਆ ਨਿੰਦਕਾ ਪਿਠਿ ਦੇਇ ਨਾਮਦੇਉ ਮੁਖਿ ਲਾਇਆ ॥
Having turned His back on the egotistical and slanderers, the Lord faced [Bhagat] Namdev”
— Adi Guru Granth Sahib, page 451
The Guru spoke poetically about these stories, which are found in Sarbloh Prakash [Granth], and are also found in the book Nirmal Pradipaka.
Following this the Guru determined, through judging their intelligence, that Bhai Karam Singh, Ganda Singh, Veer Singh, Saina Singh, and Ram Singh, these five Sikhs would go and learn Sanskrit. They pleaded with the Guru that the Brahmans might refuse to teach them having assessed them as low caste. The Guru commanded, “The House of Guru holds both Raaj [temporal] and Yog [spiritual knowledge]. So you shall wear the clothes of a Sadhu, and adopt celibacy, and then go to live in Kaashi to learn wisdom [vidiya]. With our boon and grace you shall quickly learn the wisdom of the [ancient] scriptures” With this Command, in the year 1742 Bikrami [1685CE] these five Sikhs went to Kaashi, where Bhai Gurdas previously stayed, at Chetanmath, studying vidiya [wisdom] the Nirmala Saints [sampradiya] grew in numbers. Within just one year they had become full Pandits and had returned back to Guru Gobind Singh. With great pleasure the Guru blessed them with the boons of wealth, powerful positions, saintliness, mysticism, mastery of gunas, ability to be the giver of alms, and then commanded, "All these qualities will be present within the Khalsa. From you the Guru’s Nirmala Panth will emerge.”
As time past the Guru sent countless Sikhs to learn Sanskrit from them as well as transcribing major Sanskrit works such as, Devi Bhagavad Puran, Bishan Bhagavad Puran, Mahabharat, Vishan Puran, Hitopdesh, Upanishads, Bhoj Prabhand, Sukrniti, Manu Smriti and others, into the vernacular [Brij Bhasha], out of which even now Mahabharat, Upanishads, Vishist, Hitopdesh, Chanakaa, Jaimni, Asvumedh and others, still exist. The rest were stolen or burned when the evacuation of Anandpur occurred.
- Excerpt from Twarikh Guru Khalsa [1880CE], Patshahi 10 Chapter 27. written by Giani Gian Singh.
ਤਵਾਰੀਖ ਗੁਰੂ ਖਾਲਸਾ [1880ce], ਪਾਤਿਸ਼ਾਹੀ 10, ਅਧਿਆਇ 27. ਕ੍ਰਿਤ: ਗਯਾਨੀ ਗਯਾਨ ਸਿੰਘ