One verse

Srimad Bhagavatam 6.1.54

6.1.54

लब्ध्वा निमित्तमव्यक्तं व्यक्ताव्यक्तं भवत्युत । यथायोनि यथाबीजं स्वभावेन बलीयसा ॥ ५४ ॥

labdhva nimittam avyaktam vyaktavyaktam bhavaty uta yatha-yoni yatha-bijam svabhavena baliyasa

labdhva
having gotten
nimittam
the cause
avyaktam
unseen or unknown to the person
vyakta-avyaktam
manifested and unmanifested, or the gross body and the subtle body
bhavati
come into being
uta
certainly
yatha-yoni
exactly like the mother
yatha-bijam
exactly like the father
sva-bhavena
by the natural tendency
baliyasa
which is very powerful.

The fruitive activities a living being performs, whether pious or impious, are the unseen cause for the fulfillment of his desires. This unseen cause is the root for the living entity’s different bodies. Because of his intense desire, the living entity takes birth in a particular family and receives a body which is either like that of his mother or like that of his father. The gross and subtle bodies are created according to his desire.