CHĀNDOGYA UPANISHAD · 1.11.4

अथ हैनं प्रस्तोतोपससाद ।
प्रस्तोतर् या देवता प्रस्तावम् अन्वायत्ता तां चेद् अविद्वान् प्रस्तोष्यसि मूर्धा ते विपतिष्यतीति मा भगवान् अवोचत् ।
कतमा सा देवतेति ॥

atha hainaṃ prastotopasasāda ।
prastotar yā devatā prastāvam anvāyattā tāṃ ced avidvān prastoṣyasi mūrdhā te vipatiṣyatīti mā bhagavān avocat ।
katamā sā devateti ॥

Then the Prastotri approached him, saying: 'Sir, you said to me, "Prastotri, if you, without knowing the deity which belongs to the prastâva, are going to sing it, your head will fall off,"--which then is that deity?'

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