CHĀNDOGYA UPANISHAD · 5.24.1

स य इदम् अविद्वान् अग्निहोत्रं जुहोति यथाङ्गारान् अपोह्य भस्मनि जुहुयात् तादृक् तत् स्यात् ॥

sa ya idam avidvān agnihotraṃ juhoti yathāṅgārān apohya bhasmani juhuyāt tādṛk tat syāt ॥

'If, without knowing this, one offers an Agnihotra, it would be as if a man were to remove the live coals and pour his libation on dead ashes.

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)