Markandeyapurana 48.4-6

48.4

tato devāsurān pitṝn mānuṣāṃśca catuṣṭayam /
sisṛkṣurambhāṃsyetāni svamātmānamayūyujat //

Desiring to create these four waters—gods, asuras, ancestors, and men— / he then concentrated his mind.

Then being desirous of creating the four classes of beings, namely, the gods, the Asuras and the pitṛs, and mankind, he infused[3] himself in the waters. The particle of darkness grew up in excess as the Prajāpati was rapt in meditation. First then out of his buttocks, as he was desirous of creating, were produced the Asuras. And then he cast aside that body which was composed of the particle of darkness; that body cast aside by him forthwith became Night.

48.5

yuktātmanastamomātrā udriktābhūt prajāpateḥ /
sisṛkṣorjaghanāt pūrvamasurā jajñire tataḥ //

As he disciplined his self, the measure of darkness became abundant in the Lord of Creatures; / then, from the groin of him wishing to create, asuras were born first.

48.6

utsasarja tatastāntu tamomātrātmikāṃ tanum /
sāpaviddhā tanustena sadyo rātrirajāyata //

He then cast off that body consisting of the measure of darkness. / That body, cast off by him, immediately became night.