CHĀNDOGYA UPANISHAD · 1.11.6

अथ हैनम् उद्गातोपससाद ।
उद्गातर् या देवतोद्गीथम् अन्वायत्ता तां चेद् अविद्वान् उद्गास्यसि मूर्धा ते विपतिष्यतीति मा भगवान् अवोचत् ।
कतमा सा देवता इति ॥

atha hainam udgātopasasāda ।
udgātar yā devatodgītham anvāyattā tāṃ ced avidvān udgāsyasi mūrdhā te vipatiṣyatīti mā bhagavān avocat ।
katamā sā devatā iti ॥

Then the Udgâtri approached him, saying: 'Sir, you said to me, "Udgâtri, if you, without knowing the deity which belongs to the udgîtha, 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)