Śrī brahma-saṁhitā 5.23
tat-kālaṁ kila coditaḥ
sisṛkṣāyāṁ matiṁ cakre
dadarśa kevalaṁ dhvāntaṁ
nānyat kim api sarvataḥ
sañjātaḥ — on being born; bhagavat-śaktyā — by the divine potency; tat-kālam — at that time; kila — indeed; coditaḥ — being guided; sisṛkṣāyām — to the act of creation; matim — his mind; cakre — turned; pūrva-saṁskāra-saṁskṛtaḥ — under the impulse of previous impressions; dadarśa — he saw; kevalam — only; dhvāntam — darkness; na — not; anyat — else; kim api — anything; sarvataḥ — in every direction.
On coming out of the lotus, Brahmā, being guided by the divine potency tuned his mind to the act of creation under the impulse of previous impressions. But he could see nothing but darkness in every direction.
Brahmā's impulse for creation arises solely from his previous impressions. All jīvas get their nature conformably to their impressions of previous births and accordingly their activity can have a beginning. It is called "the unseen" or the result of one's previous deeds. His natural impulse is formed according to the nature of the deeds done by him in the previous kalpa. Some of the eligible jīvas also attain to the office of Brahmā in this way.