CHĀNDOGYA UPANISHAD · 1.12.3

तान् होवाचेहैव मा प्रातर् उपसमीयतेति ।
तद् ध बको दाल्भ्यो ग्लावो वा मैत्रेयः प्रतिपालयां चकार ॥

tān hovācehaiva mā prātar upasamīyateti ।
tad dha bako dālbhyo glāvo vā maitreyaḥ pratipālayāṃ cakāra ॥

The white dog said to them: 'Come to me to-morrow morning.' Vaka Dâlbhya, or, as he was also called, Glâva Maitreya, watched.

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