Bhagavad Gita 8.25
धूमो रात्रिस्तथा कृष्णः षण्मासा दक्षिणायनम्। तत्र चान्द्रमसं ज्योतिर्योगी प्राप्य निवर्तते।।8.25।।
dhūmo rātristathā kṛṣṇaḥ ṣaṇmāsā dakṣiṇāyanam| tatra cāndramasaṃ jyotiryogī prāpya nivartate||8.25||
dhumo ratristatha krishnah shanmasa dakshinayanam tatra candramasam jyotiryogi prapya nivartate8.25
Meaning
Smoke, night, the dark fortnight, and the six months of the southern solstice — the yogi departing by this path reaches the lunar light and returns to the world.
धूम, रात्रि, कृष्णपक्ष और दक्षिणायन के छः मास वाले मार्ग से चन्द्रमा की ज्योति को प्राप्त कर, योगी लौटता है।
This is verse 25 of 28 in Chapter 8 (Aksara Brahma Yoga) of the Bhagavad Gita.