CHĀNDOGYA UPANISHAD · 3.1.3

एतम् ऋग्वेदम् अभ्यतपन् ।
तस्याभितप्तस्य यशस् तेज इन्द्रियं वीर्यम् अन्नाद्यं रसो ऽजायत ॥

etam ṛgvedam abhyatapan ।
tasyābhitaptasya yaśas teja indriyaṃ vīryam annādyaṃ raso ’jāyata ॥

Those very Rik verses then (as bees) brooded over the Rig-veda sacrifice (the flower); and from it, thus brooded on, sprang as its (nectar) essence, fame, glory of countenance, vigour, strength, and health.

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