One verse

Srimad Bhagavatam 11.4.3

11.4.3

भूतैर्यदा पञ्चभिरात्मसृष्टै: पुरं विराजं विरचय्य तस्मिन् । स्वांशेन विष्ट: पुरुषाभिधान- मवाप नारायण आदिदेव: ॥ ३ ॥

bhūtair yadā pañcabhir ātma-sṛṣṭaiḥ puraṁ virājaṁ viracayya tasmin svāṁśena viṣṭaḥ puruṣābhidhānam avāpa nārāyaṇa ādi-devaḥ

bhūtaiḥ
by the material elements
yadā
when
pañcabhiḥ
five (earth, water, fire, air and ether)
ātma-sṛṣṭaiḥ
created by Himself
puram
the body
virājam
of the universe in its subtle form
viracayya
having constructed
tasmin
within that
sva-aṁśena
in the manifestation of His own plenary expansion
viṣṭaḥ
entering
puruṣa-abhidhānam
the name Puruṣa
avāpa
assumed
nārāyaṇaḥ
Lord Nārāyaṇa
ādi-devaḥ
the original Personality of Godhead

When the primeval Lord Nārāyaṇa created His universal body out of the five elements produced from Himself and then entered within that universal body by His own plenary portion, He thus became known as the Puruṣa.