Śatapatha Brāhmaṇa ("of a hundred paths") 6.3.1.40

6.3.1.40

tribhirādatte | trivṛdagniryāvānagniryāvatyasya mātrā tāvataivaināmetadādatte tribhirādāyāthaināṃ caturthenābhimantrayata etadvā enāṃ devāstribhirādāyāthāsyāṃ caturthena vīryamadadhustathaivaināmayametattribhirādāyāthāsyāṃ caturthena vīryaṃ dadhāti

With three (formulas) he takes it up,--threefold is Agni: as great as Agni is, as great as is his measure, by so much he thus takes it. Having taken it up with three (formulas), he addresses it with a fourth; for the gods having thus taken it with three (formulas), then laid vigour into it by means of a fourth; and in like manner does he now, after taking it up with three (formulas), lay strength into it with the fourth.