1. The four formulas
"Formula" is more appropriate than "sacred prayer" (ang. holy prayer, all. heilig Gebet), the term usually used. There are four: the Ahuna Vairiia (AV), the Aṣ̌ǝm Vohū (AVo), the Yeŋ́he Hātąm (YH) and the Airiiaman Išiia (AI), placed in Geldner's edition at Y27.13 Y27.14, Y27.15 and Y54.1 respectively.
Differences between Old Avestic and Late Avestic
How do we decide whether a text is Old-Avestic or Late-Avestic? Are the four formulas part of the Old Avesta or the Late Avesta?
a) Two formal criteria for Old Avesta
a. systematic lengthening of final vowels ;
b. preservation of intervocalic sound occluders (v.av. dadāt̰ and av. rec. daδāt̰) ;
but these criteria cannot be retained, not least because they are imitable. If we applied them, all the formulas would be old-avestic.
b) Two linguistic criteria for Old-Avestic
a. preservation of the aorist (e.g. dadāt̰ opposite the aor. inj. dāt̰);
b. enclitic forms of1st and2nd pers. plural pronouns (1st pl.: v.av. acc. nå and gen.-dat. nǝ̄, but av. rec. acc.-gén.-dat. nō) ;
So the AI is old-avestic since it contains three aorists. As for the YH, it's an adaptation of Y51.22 in late-Avestic.
c) Metrics
a. The AV has the same structure (3 verses of 7 + 9 syllables) as the first Gāθā (Y28-34);
b. The AI has the same structure (2 verses of 7 + 5 syllables, then 2 verses of 7 + 7 + 5 syllables) as the last Gāθā (Y53);
The first and last stanzas of the gāthic corpus are therefore highlighted.
Their place: a dubious position in the corpus
AVo and YH occupy stanzas 14 and 15 of Y27 only in exegetical manuscripts (e.g. 500_J2, 510_K5, 400_Pt4). The YH has no precise place; it is a punctuation formula. As for the AVo, its place in the liturgical cursus is Y11.19. However, the AVo follows the AV in the case of the intercalation of the Hāδōxt Nask (HN), the first chapter of which is itself a commentary on the AVo.