CHĀNDOGYA UPANISHAD · 4.1.7

स ह क्षत्तान्विष्य नाविदम् इति प्रत्येयाय ।
तं होवाच यत्रारे ब्राह्मणस्यान्वेषणा तद् एनम् अर्च्छेति ॥

sa ha kṣattānviṣya nāvidam iti pratyeyāya ।
taṃ hovāca yatrāre brāhmaṇasyānveṣaṇā tad enam arccheti ॥

The door-keeper went to look for Raikva, but returned saying, 'I found him not.' Then the king said: 'Alas! where a Brâhmana should be searched for (in the solitude of the forest), there go for him.'

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