Adhyāya 39 — त्रिगुणविवेकः (Discrimination of the Three Guṇas) and Avyakta-Doctrine
एवं ज्योतिष्षु सर्वेषु निवर्तन्ते गुणास्त्रय: । पर्यायेण च वर्तन्ते तत्र तत्र तथा तथा,इस प्रकार सभी ज्योतियोंमें तीनों गुण क्रमश: वहाँ-वहाँ उस-उस प्रकारसे प्रकट होते और विलीन होते रहते हैं
evaṁ jyotiṣṣu sarveṣu nivartante guṇās trayaḥ | paryāyeṇa ca vartante tatra tatra tathā tathā ||
Thus, in all luminous bodies, the three guṇas repeatedly subside and reappear—taking their turns and manifesting in each place in its own particular way. The teaching is that even what seems steady and radiant is governed by cyclical change in nature, so one should discern the play of qualities rather than mistake it for an unchanging self.
वायुदेव उवाच
All phenomena—even luminous or exalted ones—are subject to the alternating dominance of sattva, rajas, and tamas. Recognizing this cyclical play helps one cultivate discernment and avoid identifying the self with changing states.
Vāyudeva is explaining a cosmological-psychological principle: across all ‘lights’ (luminous bodies or radiant manifestations), the three guṇas repeatedly manifest and withdraw in turn, differing according to context and locus.