It refers to the band of 40 brave Sikhs who laid down their lives fighting near the dhab or lake of Khidrana, also called Isharsar, on 29 December 1705 against a Mughal force in chase of Sri Guru Gobind Singh Ji who are remembered in Sikh history and daily in the Sikh ardas or supplicatory prayer offered individually or at gatherings at the end of all religious services. Sri Guru Gobind Singh Ji, who had watched the battle from a nearby mound praised the martyrs' valour and blessed them as the Chali Mukte, the "Forty Immortals" or "Forty Beloved". After them Khidrana became Muktsar, the "Pool of Liberation".

While there is no unanimity over the names of the martyrs of Muktsar and Chamkaur Sahib, the five Muktas who comprised the first batch of Sikhs to receive amrit at the hands of the Panj Piare are given in Rahitnama by Bhai Daya Singh as Ram Singh, Fateh Singh, Deva Singh, Tahil Singh and Isar Singh. No other details of these five are available except that an old manuscript of Bhai Prahlad Singh's Rahitnama is said to contain a note associating Ram Singh and Deva Singh with the village of Bughiana, Tahil Singh and Isar Singh with DallVan and Fateh Singh with Khurdpur Mangat.

According to Bhai Chaupa Singh, his Rahitnama or code of conduct was drafted by muktas. The text is said to have received Sri Guru Gobind Singh Ji's approval on 7Jeth 1757 Bk / 5 May 1700. It appears that the title of mukta was bestowed subsequently also on persons other than the original five. The number of muktas is recorded variously in old Sikh texts. For instance, Kesar Singh Chhibbar, Barisava/mama Dasari Patshahian Ka, mentions 14, and Kuir Singh, Gurbilas Patshahi X, 25.

But the forty muktas universally celebrated in the Sikh tradition are the forty martyrs of Muktsar who earned this title by sacrificing their lives for the Guru and who redeemed their past apostasy, of having disowned Sri Guru Ji and deserted him driven to desperation by the prolonged siege of Anandpur by the hill chiefs and Mughal forces, by having their disclaimer torn by the Guru as the last of them laid in the Guru's lap dying.

The names of the forty Mukte are listed below: