Śvetāśvatara Upaniṣad · 6..5
तद् वै तत् सत्यं सत्यं वै तत् सत्यस्य सत्यं तद् वै तत् सत्यं सत्यं वै तत्
tad vai tat satyaṃ satyaṃ vai tat satyasya satyaṃ tad vai tat satyaṃ satyaṃ vai tat
That in truth is the Truth. The Truth in truth is That. The Truth of truth —that in truth is the Truth. The Truth in truth is That.
Third repetition, completing a triple pattern about satya. In our yoga practice, the number three represents stability and completeness. The triple affirmation of identity between tat and satya leaves us in presence of the ineffable. This is the satya that cannot be said but can be lived, not propositional truth but the Reality that makes all proposition possible. To know this is to be amṛta, immortal.