CHĀNDOGYA UPANISHAD · 4.17.10

मानवः ।
ब्रह्मैवैक ऋत्विक् कुरून् अश्वाभिरक्षति ।
एवंविद् ध वै ब्रह्मा यज्ञं यजमानं सर्वांश् चर्त्विजो ऽभिरक्षति ।
तस्माद् एवंविदम् एव ब्रह्माणं कुर्वीत नानेवंविदं नानेवंविदम् ॥

mānavaḥ ।
brahmaivaika ṛtvik kurūn aśvābhirakṣati ।
evaṃvid dha vai brahmā yajñaṃ yajamānaṃ sarvāṃś cartvijo ’bhirakṣati ।
tasmād evaṃvidam eva brahmāṇaṃ kurvīta nānevaṃvidaṃ nānevaṃvidam ॥

viz. the Brahman only, as one of the Ritvig priests. 'He saves the Kurus as a mare' (viz. a Brahman priest who knows this, saves the sacrifice, the sacrificer, and all the other priests). Therefore let a man make him who knows this his Brahman priest, not one who does not know it, who does not know it.

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