18. avyaktad vyaktayah sarvah
tatrai 'va 'vyaktasamjnake
(18) At the coming of day, all manifested things come forth from the unmanifested and at the coming of night they merge in that same, called the unmanifested.
Here the unmanifested is prakrtl.
19. bhutagramah sa eva 'yam
ratryagame 'vasah partha
(19) This very same multitude of existences arising again and again merges helplessly at the coming of night, 0 Partha (Arjuna), and streams forth into being at the coming of day
This periodic emergence and dissolution of all existences does not affect the Lord of all existences.
20. paras tasmat tu bhavo
'nyo 'vyakto 'vyaktat sanatanah
yah sa sarvesu bhZttesu
nasyatsu na vinasyati
(20) But beyond this unrnanifested, there is yet another Unmdniflested Eternal Being who does not perish even when all existences perish.
It is the Supracosmic Unmanifested which is changeless and eternal, in the midst of all changes Two types of unmanifested are sometimes distinguished, an unmanifested (avyakta), into which all unredeemed beings enter, and the supercosmic avyakta, called also suddhatattva which is imperceptible to the ordinary mind into which the redeemed souls enter. The perpetual rhythm of day and night is on all cosmic beings which cannot last for ever. Beyond the cosmic process is the Supreme Unmanifested Brahman, the highest goal. Those who attain It pass beyond day and night.
21. avyakto 'kara ity uktas
tam ahuh parainam gating yam
praaya na nivartante tad
dhama parannam mama
(21) This Unmanifested is called the Imperishable Him they speak of as the Supreme Status. Those who attain to Him return not That is My supreme abode
We escape from the cycle of birth and death or cosmic manifestation (prabhava) and non-manifestation (pralaya). Even to reach the status of the Indefinable Absolute whose status goes beyond the cosmic manifestation, we have to offer our whole personality to the Supreme. Even the supracosmic condition of the Eternally Unmanifest can be won through bhakti or devotion By union with Him of our whole conscious being, we reach the perfect consummation. The supreme abode of the personal God, Isvara, is Parabrahma, the Absolute see also VIII, 2
22. purusah sa parah partha
bhaktya labhyas tv ananyaya
yasya 'ntahsthani bhutani
vena sarvam idam tatam
(22) This is the Supreme Person, 0 Partha (Arjuna), in whom all existences abide and by whom all this is pervaded (who) can, however, be gained by unswerving devotion
23 yatra kale tv andvrttim
dvrttim cai 'va yoginah
prayata yanti tam kalam
(23) Now I shall declare to thee, 0 Best of Bharatas (Arjuna), the time in which yogins departing, never return and also that wherein departing they return.