Śatapatha Brāhmaṇa ("of a hundred paths") 4.4.1.7

4.4.1.7

taṃ gṛhītvā na sādayati | mano ha vā asya savitā tasmādidamasannam manaḥ prāṇo ha vā asya savitā tasmādayamasannaḥ prāṇaḥ saṃcaratyathāha devāya savitre 'nubrūhītyāśrāvyāha devāya savitre preṣyeti vaṣaṭkṛte juhoti nānuvaṣaṭkaroti mano ha vā asya savitā nenmano 'gnau pravṛṇajānīti prāṇo ha vā asya savitā netprāṇamagnau pravṛṇajānīti

Having drawn it, he does not deposit it; for Savitri is his (Yagña's) mind, and hence this mind is restless. And Savitri is his breath: hence this breath passes to and fro unrestingly. He then says (to the Maitrâvaruna), 'Recite (the invitatory prayer) to the god Savitri!' Having called for the Sraushat, he says, 'Prompt (the Hotri to recite the offering prayer) to the god Savitri!' The Vashat having been pronounced, he offers. He (the Hotri) pronounces no Anuvashat,--for Savitri is his mind,--'lest he should consign his mind to the fire;' and Savitri being his breath,--'lest he should consign his breath to the fire.'