Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 42

Sanskrit:

ततोऽविशन्वनं चन्द्रज्योत्स्‍ना यावद् विभाव्यते ।तम: प्रविष्टमालक्ष्य ततो निववृतु: स्त्रिय: ॥ ४२ ॥

ITRANS:

tato ’viśan vanaṁ candrajyotsnā yāvad vibhāvyatetamaḥ praviṣṭam ālakṣyatato nivavṛtuḥ striyaḥ

Translation:

In search of Kṛṣṇa, the gopīs then entered the depths of the forest as far as the light of the moon shone. But when they found themselves engulfed in darkness, they decided to turn back.

Purport:

The gopīs entered a part of the forest so dense that even the light of the full moon couldn’t penetrate it. This scene is also described in the Viṣṇu Purāṇa: “One gopī said, ‘Kṛṣṇa has entered such a dark part of the forest that we cannot possibly see His footprints. Therefore let us turn back from this area, which even the light of the moon cannot reach.’”