CHĀNDOGYA UPANISHAD · 2.24.7
पुरा माध्यन्दिनस्य सवनस्योपाकरणाज् जघनेनाग्नीध्रीयस्योदङ्मुख उपविश्य स रौद्रं सामाभिगायति ॥
purā mādhyandinasya savanasyopākaraṇāj jaghanenāgnīdhrīyasyodaṅmukha upaviśya sa raudraṃ sāmābhigāyati ॥
Before the beginning of the Mâdhyandina-savana, the noon-oblation, the sacrificer, sitting down behind the Âgnidhrîya altar, and looking towards the north, sings the Sâman, addressed to the Rudras:
F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)