Śatapatha Brāhmaṇa ("of a hundred paths") 3.2.2.15

3.2.2.15

taddhaike | prathame vrate sarvauṣadhaṃ sarvasurabhyāvapanti yadi dīkṣitamārtirvindedyenaivātaḥ kāmayeta tena bhiṣajyedyathā vratena bhiṣajyediti tadu tathā na kuryānmānuṣaṃ ha te yajñe kurvanti vyṛddhaṃ vai tadyajñasya yanmānuṣaṃ nedvyṛddhaṃ yajñe karavāṇīti yadi dīkṣitamārtirvindedyenaivātaḥ kāmayeta tena bhiṣajyetsamāptirhyeva puṇyā

Some, again, add to the first (day's) fast-food (vrata) all manner of vegetables and fragrant (seasoning), arguing,--'If disease were to befall him, he might cure it by whatever thereof he pleases, as if he cured it by the fast-milk.' But let him not do this, lest he should do what is inauspicious to the sacrifice; for those people do at the sacrifice what is a human act, and inauspicious to the sacrifice assuredly is that which is human. If any disease were to befall him who is consecrated, let him cure it wherewith he pleases; for completion is proper.