Chandogya Upanishad 2.22.5

2.22.5

sarve svarā ghoṣavanto balavanto vaktavyā indre balaṃ dadānīti \
sarva ūṣmāṇo 'grastā anirastā vivṛtā vaktavyāḥ prajāpater ātmānaṃ paridadānīti \
sarve sparśā leśenānabhinihitā vaktavyā mṛtyor ātmānaṃ pariharāṇīti \\222.5\

5. All the vowels should be pronounced strong and sonant, with the thought: ‘To Indra let me give strength.’ All the spirants should be pronounced well open, without being slurred over, without being elided, with the thought: ‘To Prajāpati let me entrust myself.’ All the [other] consonants should be pronounced slowly, without being merged together, with the thought: ‘From Mṛityu (Death) let me withdraw myself (*ātman*).’