Srimad Bhagavatam — Tritiya Skandha, Shloka 26
Kāla-vibhāga: The Divisions of Time from Atom to Brahmā, and the Lord Beyond Time
एष दैनन्दिन: सर्गो ब्राह्मस्त्रैलोक्यवर्तन: । तिर्यङ्नृपितृदेवानां सम्भवो यत्र कर्मभि: ॥ २६ ॥
eṣa dainan-dinaḥ sargo brāhmas trailokya-vartanaḥ tiryaṅ-nṛ-pitṛ-devānāṁ sambhavo yatra karmabhiḥ
这就是梵天之日的日常创造，使三界（天界、世间、地下界）运转不息；其中畜生、人类、祖灵（Pitṛ）与诸天，皆依其业行而生起与消逝。
FAQs
It explains that there is a recurring, day-by-day manifestation under Brahmā’s administration, through which the three worlds continue their cycles of activity and population.
This verse states that births across these categories occur according to one’s own karmic actions, which shape the suitable realm and body for experience and consequence.
It encourages mindful, dharmic choices—since actions have shaping power—so one cultivates higher qualities and a trajectory favorable for spiritual progress.