KAṬHA UPANISHAD · 1.1.7

वैश्वानरः प्रविशत्यतिथिर्ब्राह्मणो गृहान् ।
तस्यैताँ शान्तिं कुर्वन्ति हर वैवस्वतोदकम् ॥ ७॥

vaiśvānaraḥ praviśatyatithirbrāhmaṇo gṛhān ।
tasyaitām̐ śāntiṃ kurvanti hara vaivasvatodakam ॥ 7॥

“Fire is the Brahmin who enters as a guest the houses of men; him thus they appease. Bring, O son of Vivasvan, the water of the guest-rite.