The original spelling for the name in Sanskrit literature is Khaśa while variants of name also used are Khasa, Khaṣa and Khaśīra.
Indian sources
Pre-historic literature
The Manusmriti states that the Khasas and several other tribes like the Sakas, Yavanas, Kambojas, Paradas, Daradas, Pahlavas, etc. were originally noble Kshatriyas, but later, due to their non-observance of valorous Kshatriya codes and neglect of chivalry, they had gradually sunken to the status of Mlechchas. Thus, it describes them as descendants of outcast Kshatriyas. The Bhagavata Purana describes them as a previously outcast group who redeemed themselves by adopting Vaishnavism. The Mahabharata mentions the Khasas as one of the northern tribes who fought on the side of the Kaurava against Satyaki. In the Karna Parva of Mahabharata, Khasas are mentioned living in the Panjab region between Āraṭṭa and Vasāti: In the Sabhaparvan of the Mahabharata, they are mentioned between Meru and Mandara along with Kulindas and Tanganas. In Dronaparvan of the Mahabharata, they are mentioned with other northwestern tribes such as Daradas, Tanganas, Lampakas and Kulindas. The Vaishnava text Harivamsa describes that the Khasas were defeated by the King Sagara. The Markandeya Purana states that the Khasa is a country against the mountain. The Markandeya Purana, Vayu Purana and Kalki Purana describes that Khasas together with Sakas and other tribes have penetrated to the northwest of India. The Skanda Purana mentions the region of Himachal Pradesh and Kumaon-Garhwal as Kedare-Khasa-Mandale.
Medieval literature
The Brihat Samhita authored by Indian polymath Varāhamihira grouped Khasas with Kulutas, Kashmiras, Tanganas, and Kunatas. The Mudrarakshasa of Indian poet Vishakhadatta mentions that Khasas and Magadhas were Ganas in the army of Rakshasa and Malayaketu. According to an ancient Kashmiri text Nilamata Purana compiled by Indian scholar Ved Kumari Ghai, the Khasa tribe occupied This assertion is also corroborated by the later 12th century text Rajatarangini translated by British archaeologist Sir Marc Aurel Stein. The Bharata Nātyaśāstra by the Indian musicologist Bharata Muni mentions that the mother tongue language of Khaśas was Bāhliki language in the phrase The Kavyamimamsa of Rajashekhara mentions the Kuluta king with the title Khasadhipati. The inscription of Dadda II mentions about the Khasas in the phrase "...Yascopamiyate - sat - kataka - samunnata vidhyadharavasa taya Himachale na Khasa parivarataya." A Jain literature Vasudevahindi by Sanghadasa narrates the travel of a merchant named Charudatta in the countries of Khasas, Hunas and Cinas. He further locates them at the northeastern direction of Indus river.
European sources
Geographer Pliny noted that E.T. Atkinson speculated that Pliny referred the terms, Cesi and Catriboni to Khasa and Kshatriya. Greek Geographer Ptolemy contended that the country of Khasas was located near the Trans-Himalayan range of Northwest India.
Tibetan sources
The Mongolian-Tibetan historian :de:Sumpa Yeshe Peljor|Sumpa Yeshe Peljor lists the Khasas alongside other peoples found in Central Asia since antiquity, including the Yavanas, Kambojas, Tukharas, Hunas and Daradas.
Descendants
Irish linguist Sir G.A. Grierson asserted that "..the great mass of the Aryan speaking population of the lower Himalaya from Kashmir to Darjeeling is inhabited by tribes descended from the ancient Khasas of Mahabharata."
The 12th-century text Rajatarangini translated by British archaeologist Sir Marc Aurel Stein links the Khasas with northwestern affiliations. It describes at Rajatarangini describes the rulers of Rajapuri as the "lord of the Khasas". It also describes the chiefs of the Lohara as Khasas. The Khasa chiefs of Rajapuri freely intermarried with Kshatriya rulers of Kashmir while the Khasa chief of Lohara, Simharaja, married a daughter of Shahi Kings of Kabul. The descendants of the royal family of Rajauri later became Muslim Rajput chiefs and they retained the rulership of the territory till 19th century. Stein also identified the modern Khakhas as descdendants of Khasas mentioned in the Rajatarangini.