CHĀNDOGYA UPANISHAD · 1.10.10

एवम् एवोद्गातारम् उवाच ।
उद्गातर् या देवतोद्गीथम् अन्वायत्ता तां चेद् अविद्वान् उद्गास्यसि मूर्धा ते विपतिष्यतीति ॥

evam evodgātāram uvāca ।
udgātar yā devatodgītham anvāyattā tāṃ ced avidvān udgāsyasi mūrdhā te vipatiṣyatīti ॥

In the same manner he addressed the Udgâtri: 'Udgâtri, if you, without knowing the deity which belongs to the udgîtha (the hymns of the Udgâtri), are going to sing it, your head will fall off.'

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