Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.4.7

3.2.4.7

tadvā etadubhayaṃ deveṣvāsīt | somaśca vākca sa yatsomaṃ krīṇātyāgatyā evāgatena yajā ityanāgatena ha vai sa somena yajate yo 'krītena yajate

Both Soma and Vâk were thus with the gods. Now, when he buys Soma he does so in order that he may sacrifice with him, when obtained, for his (own) obtainment (of heavenly bliss); for he who sacrifices with Soma that has not been bought, sacrifices with Soma that has not been (properly) obtained.