Chandogya Upanishad 1.10.10

1.10.10

evam evodgātāram uvāca \
udgātar yā devatodgītham anvāyattā tāṃ ced avidvān udgāsyasi mūrdhā te vipatiṣyatīti \\110.10\ evam eva pratihartāram uvāca \
pratihartar yā devatā pratihāram anvāyattā tāṃ ced avidvān pratihariṣyasi mūrdhā te vipatiṣyatīti \
te ha samāratās tūṣṇīm āsāṃ cakrire \\110.11\

In the same manner he addressed the Pratihartṛ priest, 'O Pratihartṛ, if you sing the Pratihāra without knowing the deity that belongs to the Pratihāra, your head will fall down.' Then they all sat down silently suspending their duties.

'O Prastotṛ, if you sing the Prastāva without knowing the deity that belongs to the Prastāva, your head will fall down.'

In the same manner he addressed the Udgātṛ priest, 'O Udgātṛ, if you sing the Udgītha without knowing the deity that belongs to the Udgītha, your head will fall down.'