Chapter 8 · verse 25 · gita.yoga.org

Bhagavad Gita 8.25

धूमो रात्रिस्तथा कृष्णः षण्मासा दक्षिणायनम्। तत्र चान्द्रमसं ज्योतिर्योगी प्राप्य निवर्तते

Attaining the lunar light through smoke, night time, the dark fortnight, and the six months of the southern path of the sun (the southern solstice), the yogi returns.