One verse

Srimad Bhagavatam 3.6.19

3.6.19

मेढ्रं तस्य विनिर्भिन्नं स्वधिष्ण्यं क उपाविशत् । रेतसांशेन येनासावानन्दं प्रतिपद्यते ॥ १९ ॥

medhram tasya vinirbhinnam sva-dhisnyam ka upavisat retasamsena yenasav anandam pratipadyate

medhram
genitals
tasya
of the gigantic form
vinirbhinnam
being separated
sva-dhisnyam
own position
kah
Brahma, the original living creature
upavisat
entered
retasa amsena
with the part of the semen
yena
by which
asau
the living entity
anandam
sex pleasure
pratipadyate
experiences.

When the genitals of the gigantic form separately became manifest, then Prajapati, the original living creature, entered into them with his partial semen, and thus the living entities can enjoy sex pleasure.