We have seen in earlier slokas that the world is not permanent, nor the activities in the world, which result in happiness or sorrow, as everything is an illusion in the substratum of brahmam. Hence we have to turn our attention to the ultimate reality of brahmam of nature of sat chit ananda. Lord Krishna says that its the ultimate goal of human life in earlier slokas and also mentions the path that would lead one to the ultimate truth.
He further elaborates about the goal that should be targeted by one and all in the next sloka. Because only this will pull us out of this chain of birth and death.
15.6 – Na Tat bhasayathee suryah na sasankah na paavakahah
Yat gatva na nivartantee tat dhamam param mama
Meaning of words:
Na tat – not that
bhasayathee – shines/illumines
suryah – the sun
sasankah – the moon
paavakaha – the fire
Yat gatva--- reaching which
Na nivartantee--- will not return back
Tat – that
Dhamam – abode
Param – supreme
Mama – is me
Meaning of sloka
The moon doesn’t shine, nor the sun shines after attaining the state of self realization , after reaching which there is no return. This supreme abode is me or brahmam.
Lord Krishna explains the state of self realization here. In this state neither the sun or the moon shines as these are part of the illusionary world. A person who is realized is above all this. This also means that when a person is realized, he is the self, the brahmam ,which illuminates the world around it. So it outshines the sun and the moon. We do not see stars during the day ,not because that the stars are not present during the day, but because the sunlight doesn’t make them visible to our eyes. So brahmam, illumines itself, nothing can illumine it, and it outshines everything. Also the brahmam is the supreme cause of the whole universe. Hence both sun and moon derive the light from brahmam, hence sun or the moon cannot illumine the brahmam , which is the cause of illumination of the entire universe. As the source of light cannot be illuminated, hence its said that sun or the moon doesn’t shine. This state , being in brahmam is described to be the state ,after attaining which there is no return. After self realization, one is always in a blissful state. He is immune to the world. As after tasting something delicious one would want to have it all the time, as one would want to enjoy it all the time and ever be happy, so also after attaining the state of eternal bliss ,one would never return , to the impermanent world filled with sorrow.