CHĀNDOGYA UPANISHAD · 5.10.8

अथैतयोः पथोर् न कतरेणचन तानीमानि क्षुद्राण्य् असकृदावर्तीनि भूतानि भवन्ति जायस्व म्रियस्वेति ।
एतत् तृतीयं स्थानम् ।
तेनासौ लोको न संपूर्यते ।
तस्माज् जुगुप्सेत ।
तद् एष श्लोकः ॥

athaitayoḥ pathor na katareṇacana tānīmāni kṣudrāṇy asakṛdāvartīni bhūtāni bhavanti jāyasva mriyasveti ।
etat tṛtīyaṃ sthānam ।
tenāsau loko na saṃpūryate ।
tasmāj jugupseta ।
tad eṣa ślokaḥ ॥

'On neither of these two ways those small creatures (flies, worms, &c.) are continually returning of whom it may be said, Live and die. Theirs is a third place. 'Therefore that world never becomes full (cf. V, 3, 2). 'Hence let a man take care to himself! And thus it is said in the following Sloka:--

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