Garudapurana 1.48.86

1.48.86

evaṃ homavidhiṃ kṛtvā nyasenmantrāṃstu deśikaḥ /
caraṇāvagnimīḷe tu iṣetvo gulphayoḥ sthitāḥ //

Having thus performed the fire offering rite, the spiritual master should place the mantras: / "agnimīḷe..." on both feet, and "iṣe tvorje..." situated upon the ankles;