O prince of the Bharata race, now I shall tell thee of the time (path) travelling in which the yogis return, and also of that taking which they do not return. (Bhagavad Gita 8.23)
Fire, light, daytime, the fortnight of waxing moon, the six months of the sun’s northern course — departing at such time, the knowers of Brahman go to Brahman. (Bhagavad Gita 8.24)
Smoke, night-time, the fortnight of waning moon, the six months of the sun’s southern course — the yogi departing at such time and attaining the lunar light returns. (Bhagavad Gita 8.25)
Bhagavan Sri Krishna describes here how and when jnana yogis and karma yogis depart from this world. The two paths described are the devayana and the pitriyana, the path of the gods and the path of the ancestors, by which the souls of the dead travel to the other world. The exact meaning, however, is not very clear. Some are inclined to think that each step means a sphere. Agni, fire, is the name of one sphere, light the name of the next and so on. While others take it to mean a state of consciousness, still others think that a state of gradual development of illumination and renunciation is meant by the light path and increasing ignorance and attachment by the dark path. It is difficult to know which is right.
At the time of death, it is said, the souls are guided by divinities to their temporary celestial abodes. These divinities are the god of fire and the god of light, the god presiding over the fortnight of waning moon and so on.
Those who, after hearing from sacred authority what Brahman is, engage in worship of Brahman, will go by the path of light and in course of time reach Brahmaloka. And at the end of the kalpa they will get mukti. This is for those who have not quite realized the Absolute in this life, but who are trying for that, and who leave the body before succeeding in the attempt. To know that Absolute, time, space and causation must go. For those who have gone beyond time and space, there can be no going or coming, here or there, this or that. These ideas are within ourselves. What we see in the external is the projection from inside. Mukti is not a question of going, but of realizing and becoming. It is a state of consciousness; it is replacement of false consciousness by true consciousness. It all depends on our thinking.
The moment we realize that we are eternal, time is conquered; the moment we realize that we are omnipresent, space is annihilated; the moment that we realize that we are changeless, we rise beyond mortality. These are all perceptions, experiences. We can perceive; we can experience eternity even during life in the body. We can see omnipresence even now, here on earth. These experiences are called states of samadhi.
Source - Reflections on the Bhagavad Gita by Swami Atulananda – Prabuddha Bharata February 2004 issue.