Garudapurana 1.218.6

1.218.6

oṃ siddhamidamāsanam iha siddhamityabhidhāya oṃ bhūḥ oṃ bhuvaḥ oṃ svaḥ oṃ mahaḥ oṃ janaḥ oṃ tapaḥ oṃ satyamiti saptavyāhṛtibhiḥ pūrvamukhandevabrāhmaṇopaveśanam /
uttaradiṅmukhaṃpitṛbrāhmayoṇopaveśanam /
oṃ devatābhyaḥ pitṛbhyaśca mahāyogibhya eva ca /
namaḥ svadhāyai svāhāyai nityameva bhavantute iti trirjapet //

Saying, "Om, this seat is prepared; it is prepared here," with the seven sacred utterances, "Om bhūḥ, Om bhuvaḥ, Om svaḥ, Om mahaḥ, Om janaḥ, Om tapaḥ, Om satyam," the brāhmaṇa representing the gods is seated facing east. / The brāhmaṇa representing the ancestors is seated facing north. / One should mutter three times: "Om, reverence to the deities and to the ancestors, and to the great yogins; / reverence to svadhā, to svāhā; may they always be for you."