Śvetāśvatara Upaniṣad · 3..11
यः स्वप्ने तिष्ठन् यं स्वप्नो न वेद यस्य स्वप्नः शरीरं यः स्वप्नेऽन्तरो यमयत्येष त आत्मान्तर्याम्यमृतः
yaḥ svapne tiṣṭhan yaṃ svapno na veda yasya svapnaḥ śarīraṃ yaḥ svapne'ntaro yamayaty eṣa ta ātmāntaryāmy amṛtaḥ
He who, dwelling in dream, whom dream does not know, whose body is the dream, who controls the dream from within —He is your Ātman, the Inner Ruler, the Immortal.
In svapna (dream), we create entire worlds without perceiving their creator. The characters in our dreams do not know they are products of our mind. Such is the relationship between antaryāmin and dream: he inhabits it, controls it, but the dream does not know him. In our yoga practice, contemplating the dream state reveals that we are the creator of experiences, not just their receiver. Lucid dreaming and yoga nidrā practice bring us closer to this understanding: I can be conscious within the dream, witness of its creation.