O Partha, the same multitude of beings being born again and again, merge in spite of themselves (into the unmanifest) at the approach of night and again manifest at the approach of day. (Bhagavad Gita 8.19)
Wsee here what Vedanta teaches regarding creation. It is not creation out of nothing, but projection from the unmanifest into the manifest state, and back again: evolution and involution. The same mass of manifestation, which we call the universe, existed in the preceding kalpa, or age, came into being at the coming of Brahma’s day and is dissolved again at the coming of night. This is an eternal process all beings are forced to follow in spite of themselves, but according to their own karma. This universe rises up and subsides, like billows on the ocean. Nothing is lost. As it sinks down, so it rises again. This occurs to entire nature, and all that is subject to nature must follow suit. As long as we are under maya, we follow this process.
Our egotism, our likes and dislikes, our fear of the unknown, our false consciousness of separation from the Spirit — all these form themselves into the endless stream of cause and effect, which flows on irresistibly. The wise alone perceive this evil, and they wish not for conditioned existence. They want to go beyond involution and evolution. They want to be free from the laws of nature.
We must remember that this going and coming is said of the jiva, not the Spirit. The Spirit comes in contact with matter and then comes into existence as the jiva, the individual soul. It is this jiva that lives in a body and then departs and is born again, but never the Spirit.