This article argues that the Yasna Haptaŋhāiti constituted the kernel of a ritual text recited during the Yasna ceremony. Zaraθušhtra's Gathas were arranged around it, and so were the holy prayers and later additions in Younger Avestan. The arrangement of the extant Older Avesta is probably the original one, and may go back to the composer himself. Its compositional principle is that of parallelism and ring composition, a pattern which can be found both in individual Gathic hymns, two of which (Y 28 and 43) are analysed, and in the structure of the entire Yasna.