agnir jyotir ahah suklah
tatra prayata gacchanti
brahma brahma-vido janah
(Attaining the Supreme, Text 24, Chapter 8)
Meaning: Those who know the Supreme Brahman attain that Supreme by passing away from the world during the influence of the fiery god, in the light, at an auspicious moment of the day, during the forthnight of the waxing moon, or during the six months when the sun travels in the north.
Bhagavad Gita: Knower of Supreme Brahman (Attaining the Supreme,Text 24, Chapter 8)