There are strict injunctions against the misuse of words, employment of corrupt words, and above all the mispronunciation of words. A priest was obliged to perform an expiatory rite called sarasvati if he pronounced a word wrongly, especially during a sacrifice.
It was believed that even a minute error in pronunciation could transform an ordinary verse into an abhichara, a spell or enchantment. The asuras (aborigines) who tried to imitate the Brahmins in performing sacrifices often mispronounced words and misplaced accents. For example, in one ceremony undertaken to gain victory over the gods, they pronounced `arayah' like `helaya', and so failed to obtain the benefit of the sacrifice and suffered defeat.
Another legend states that a Brahmin while petitioning the gods for the gift of immortality, accidentally stressed the wrong word and was condemned to eternal sleep. Yet another legend, in the Satapatha Bralunana, tells how a demon while uttering a curse against Indra, instead of saying Indrashatru, 'enemy of Indra', with accent on shatru, laid the stress on Indra, meaning, 'who has Indra for an enemy', and was struck dead. Manu Vaivasvata mispronounced a formula and got a daughter instead of a son.
The oldest treatises on the grammar and phonetics pertaining to the various shakhas of the Vedas are phonetic handbooks have helped Vedas from greater mutilation and corruption. Present-day recitation corresponds to the rules given in the pratishakhyas. There are four such treatises extant: one for the Rig-veda, ascribed to shaunaka, grandson of Gritsamad, two for yajurveda, one relating to the Black yajur-veda and one to the white, the latter ascribed to katyayana and finally, one for the Atharva-veda, also attributed to Shaunaka.
The Parishishta is a supplement or appendix, applied specifically to a post-sutra work which gives additional and rather superficial information on theological and ritualistic matters on vedic interest.