Srimad-Bhagavatam: Canto 3 - Chapter 1 - Verse 46

Sanskrit:

ते तु तज्जगृहू रूपं त्यक्तं यत्परमेष्ठिना ।मिथुनीभूय गायन्तस्तमेवोषसि कर्मभि: ॥ ४६ ॥

ITRANS:

te tu taj jagṛhū rūpaṁtyaktaṁ yat parameṣṭhināmithunī-bhūya gāyantastam evoṣasi karmabhiḥ

Translation:

The Kimpuruṣas and Kinnaras took possession of that shadowy form left by Brahmā. That is why they and their spouses sing his praises by recounting his exploits at every daybreak.

Purport:

The time early in the morning, one and a half hours before sunrise, is called brāhma-muhūrta. During this brāhma-muhūrta, spiritual activities are recommended. Spiritual activities performed early in the morning have a greater effect than in any other part of the day.