Śatapatha Brāhmaṇa ("of a hundred paths") 1.7.2.7

1.7.2.7

tadvai caturavattam bhavati | idaṃ vā anuvākyātha yājyātha vaṣaṭkāro 'tha sā devatā caturthī yasyai devatāyai havirbhavatyevaṃ hi devatā avadānānyanvāyattā avadānāni vā devatā anvāyattānyatiriktaṃ ha tadavadānaṃ yatpañcamaṃ kasmā u hi tadavadyettasmāccaturavattam bhavati

Now this (oblation) consists of four cuttings; (the reason for this is, that) there is here first, the invitatory prayer (anuvâkyâ), then the offering-prayer (yâgyâ), then the vashat-call, and as the fourth, the deity for which the sacrificial food is (destined): for in this way the deities are dependent on the sacrificial portions, or the portions are dependent on the deities: hence what fifth cutting there is (made by some), that is redundant, for--for whom is he to cut it? For this reason it consists of four cuttings.