The Pāli texts used in the paritta rites form a separate text consisting of twenty-nine sūtras of mixed length. While all these belong to different texts of the five Nikāya collections, the majority are associated with individual instances of healing or blessing. All such texts may have been incorporated into a single text after the paritta attained ritual significance.
"Paritta." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (February 19, 2018). http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/paritta
"Paritta." The Concise Oxford Dictionary of World Religions. . Retrieved February 19, 2018 from Encyclopedia.com: http://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/paritta