Hardas Singh, the grandfather of Jassa Singh, a carpenter by caste, was the resident of Sur Singh which is situated about nineteen miles east of Khem Karan, in the present district of Amritsar. Hardas Singh was initiated into the Khalsa faith by Guru Gobind Singh himself from whose hands he took pahul and fought some battles at the Guru's side. When Banda Bahadur organised the Sikhs to fight against the Mughals, Hardas Singh joined his followers and participated in most of the battles fought by him. He died in the battle of Bajwara (Hoshiarpur) AD 1715.

Source: http://en.wikipedia.org/wiki/Tarkhan_(tribe)

Bhai Hardas jee, the Hazoori Likhaari of Siri Guru Gobind Singh jee

Bhai Hardaas jee was one of the 4 main Hazoori Likhaaris of Siri Dasmesh jee and the Bir written by him, which was safe in the Sikh Reference Library up until 1984, is considered to be one of the most Shudh handwritten Saroop of Guru Sahib. In the end of this Bir written by Bhai Hardaas jee, the following words appear, that show the Avastha and humility of Bhai Sahib:

ਗ੍ਰੰਥ ਸੰਪਰੂਨ ਹੋਆ, ਲਿਖਿਆ ਹਰਿਦਾਸ ਲਿਖਾਰੀ, ਸ੍ਰੀ ਗੁਰੂ ਗੋਬਿੰਦ ਸਿੰਘ ਜੀ ਦੇ ਲਿਖਾਰੀ ਲਿਖਿਆ। ਭੁਲ ਚੁਕ ਹੋਵੇ ਸੋ ਸੋਧਨਾ, ਗੁਲਾਮ, ਪਤਿਤੁ, ਅਘ ਪਤਿਤੁ ਮਹਾਂ, ਪਤਤ ਹਰਿਦਾਸ ਲਿਖਾਰੀ ਸ੍ਰੀ ਗੁਰੂ ਗੋਬਿੰਦ ਸਿੰਘ ਜੀ ਦਾ।

- From an article by Kulbir Singh, http://www.gurmatbibek.com/contents.php?id=488