Shatapatha Brahmana 13.5.1.18

13.5.1.18

ete uddhṛtya mā no mitro varuṇo aryamāyurityetatsūktamadhrigāvāvapati catustriṃśadvājino devabandhorityu haika etām vaṅkrīṇām purastāddadhati nedanāyatane praṇavaṃ dadhāmetyatho nedekavacanena bahuvacanam vyavāyāmeti na tathā kuryātsārdhameṣa sūktamāvapedupa prāgācasanam vājyarvopa prāgātparamaṃyatsadhasthamiti

Having omitted these two (verses), he inserts the hymn (I, 162), 'Never (shall forget us) Mitra, Varuna, Aryaman, Âyu...,' in the Adhrigu (litany). Some, however, insert this verse (I, 162, 18), 'Thirty-four (ribs) of the steed, akin to the gods, (doth the knife hit)...,' before the (passage,--'twenty-six are its) ribs,' thinking lest they should place the holy syllable 'om' in the wrong place, or lest they should suggest the plural by a singular. Let him not proceed thus, but let him insert the hymn as a whole.--'The swift racer hath gone forward to the slaying...'--'The racer hath gone forward to the highest place...'--