Śatapatha Brāhmaṇa ("of a hundred paths") 1.6.3.23

1.6.3.23

dvayaṃ vā idaṃ na tṛtīyamasti | ārdraṃ caiva śuṣkaṃ ca yacuṣkaṃ tadāgneyaṃ yadārdraṃ tatsaumyamatha yadidaṃ dvayamevāpya kimetāvatkriyata ityagnīṣomayorevājyabhāgāvagnīṣomayorupāṃśuyājo 'gnīṣomayoḥ puroḍāśo yadata ekatamenaivedaṃ sarvamāpnotyatha kimetāvatkriyata ityagnīṣomayorhaivaitāvatī vibhūtiḥ prajātiḥ

Twofold, verily, is this, there is no third: to wit, the moist and the dry; and what is dry, that relates to Agni; and what is moist, that relates to Soma. But (it may be objected) if this is twofold only, why then this manifold performance:--the two butter-portions for Agni and Soma, the low-voiced offering to Agni and Soma, and the rice-cake for Agni and Soma,--when by means of any one of these he obtains all, why then this manifold performance? [The answer to this objection is that] so manifold is the power, the generative force of Agni and Soma.