SATI or sachch, Punjabi form of the Sanskrit satya or sat, lit. truth, in the philosophical sense is essential and ultimate reality as against inessential or partial truth. Rooted in Sanskrit as meaning "to be, live, exist, be present, to abide, dwell, stay", satya means " true, real, pure," as also the "quality of being abidingly true, real, existent." Satya or satyam is a widely used term in the philosophical thought of India. It signifies eternality, continuity and unicity. In the Upanisads sat (truth) is the first of the three essential characteristics of Brahman, the other two being chit (intelligence) and anand (bliss). In Vedanta philosophy, the one permanent reality, Brahman, is called Sat, while the phenomenal fluxional world is named asat (nonreal).
SATI DAS, BHAI (d. 1675), the martyr, was the younger brother of Diwan Mati Das. According to Bhatt Vahl Talauda he served Guru Tegh Bahadur as a cook. He was, under imperial warrant, detained along with the Guru at Dhamtan, as the latter was travelling to the eastern parts in 1665. He was again in attendance upon the Guru when, in 1675, the latter lefl Anandpur resolved to court martyrdom. The Guru and his companions were arrested on the way and taken to Delhi. Like his brother Mati Das, Sati Das refused to perjure his faith and was tortured to death. Wrapped up in cotton wool, he was set afire and roasted alive. This happened on 11 November 1675 the day Guru Tegh Bahadur was executed.
AKAL, lit. timeless, immortal, non temporal, is a term integral to Sikh tradition and philosophy. It is extensively used in the Dasam Granth hymns by Guru Gobind Singh, who titled one of his poetic compositions Akal Ustati, i.e. In Praise (ustati) of the Timeless One (akal). However, the concept of Akal is not peculiar to the Dasam Granth. It goes back to the very origins of the Sikh faith. Guru Nanak used the term in the Mul Mantra, the fundamental creedal statement in the Japu, the first composition in the Guru Granth Sahib.