Srimad Bhagavatam Canto 11, Chapter 28, Text 20

SB 11.28.20

vijñanam etat triy-avastham anga
 guna-trayam karana-karya-kartr
samanvayena vyatirekatas ca
 yenaiva turyena tad eva satyam
The material mind manifests in three phases of consciousness — wakefulness, sleep and deep sleep — which are products of the three modes of nature. The mind further appears in three different roles — the perceiver, the perceived and the regulator of perception. Thus the mind is manifested variously throughout these threefold designations. But it is the fourth factor, existing separately from all this, that alone constitutes the Absolute Truth.
As stated in Katha Upanisad (2.2.15), tam eva bhantam anubhati sarvam/ tasya bhasa sarvam idam vibhati: “Everything radiates its illumination in pursuance of His original illumination; His light illuminates everything in this universe.” As thus described, the entire range of perception, cognition and sensitivity is an insignificant expansion of the perception, cognition and sensitivity of the Personality of Godhead.
Srimad Bhagavatam Canto 11, Chapter 28, Text 19
Srimad Bhagavatam Canto 11, Chapter 28, Text 21