Praśna Upaniṣad ("Six Questions") 5.6

5.6

tisro mātrā mṛtyumatyaḥ prayuktā anyonyasaktā anaviprayuktāḥ
kriyāsubāhyābhyantaramadhyamāsusamyakprayuktāsuna kampate jñaḥ

6. The three elements are deadly when employed
One after the other, separately.
In actions external, internal, or intermediate
When they are properly employed, the knower trembles not.
7. With the Rig verses, to this world; with the Sāman chants, to the intermediate space;
With the Yajus formulas, to that which sages (*kavi*) recognize;
With the syllable *Om* in truth as a support, the knower reaches That
Which is peaceful, unaging, immortal, fearless, and supreme!’