Bhagavatapurana 9.6.27

9.6.27

rājā tadyajñasadanaṃ praviṣṭo niśi tarṣitaḥ /
dṛṣṭvā śayānān viprāṃstān papau mantrajalaṃ svayam //

27. At midnight the king became thirsty and entered into the sacrificial sanctorium and, seeing all the brahmins asleep, he himself drank the water which had been consecrated with mantras.