Bg. 14.15

रजसि प्रलयं गत्वा कर्मसङ्गिषु जायते ।
तथा प्रलीनस्तमसि मूढयोनिषु जायते ॥१५॥

Text

rajasi pralayaṁ gatvā
karma-saṅgiṣu jāyate
tathā pralīnas tamasi
mūḍha-yoniṣu jāyate

Synonyms

rajasiplugin-autotooltip__small plugin-autotooltip_bigrajasi

in passion; in the mode of passion.
—in passion; pralayamplugin-autotooltip__small plugin-autotooltip_bigpralayam

dissolution.
—dissolution; gatvāplugin-autotooltip__small plugin-autotooltip_biggatvā

after going; approaching; attaining; going; going there; having approached; having gone; on returning.
—attaining; karmaplugin-autotooltip__small plugin-autotooltip_bigkarma

karma; according to work; act; action; actions; activities (to support the Daityas); activities; activities being dedicated to You; activities of service to You; activity; activity of life; acts; and activities; and fruitive activities; and work; another activity; by actions; by activities; by fruitive activities; by predestined resultant actions; by wonderful activities, pious activities; by work; duties; duty; fruitive action; fruitive activities; fruitive activity; fruitive desires; fruitive work; in activities; material activities; my deeds; of activities; of fruitive activities; of the activities; one's prescribed activities; pastimes; pastimes, activities; prescribed duties; prescribed duty; reaction of the past; reactionary work; story; such service to the master; the accomplishment; the act; the activities; the activity; the business; the fate of the living entity; the fruits of action; the fruits of activities; the interaction; the objective; the sacrifice; these activities; to such activities; transcendental activity; uncommon deeds; whose transcendental activities; work.
-saṅgiṣuplugin-autotooltip__small plugin-autotooltip_bigsaṅgiṣu

in the association of fruitive activities.
—in the association of fruitive activities; jāyateplugin-autotooltip__small plugin-autotooltip_bigjayate

one becomes victorious.
—takes birth; tathāplugin-autotooltip__small plugin-autotooltip_bigtatha

so.
—thereafter; pralīnaḥplugin-autotooltip__small plugin-autotooltip_bigpralīnaḥ

being dissolved.
—being dissolved; tamasiplugin-autotooltip__small plugin-autotooltip_bigtamasi

darkness; in darkness; in hellish life; in ignorance; in the darkness; in the darkness of illusion; in the material existence of darkness; into hell; into the darkness of ignorance; of the mode of ignorance; when the darkness.
—in ignorance; mūḍhaplugin-autotooltip__small plugin-autotooltip_bigmudha

surpassed; uselessly.
—animal; yoniṣuplugin-autotooltip__small plugin-autotooltip_bigyoniṣu

in different species of life; in families; in the wombs; species.
—species; jāyateplugin-autotooltip__small plugin-autotooltip_bigjayate

one becomes victorious.
—take birth. 

Translation

When one dies in the mode of passion, he takes birth among those engaged in fruitive activities; and when he dies in the mode of ignorance, he takes birth in the animal kingdom. 

Purport

Some people have the impression that when the soul reaches the platform of human life, it never goes down again. This is incorrect. According to this verse, if one develops the mode of ignorance, after his death he is degraded to the animal form of life. From there one has to again elevate himself, by evolutionary process, to come again to the human form of life. Therefore, those who are actually serious about human life should take to the mode of goodness and in good association transcend the modes and become situated in Kṛṣṇa consciousness. This is the aim of human life. Otherwise, there is no guarantee that the human being will again attain to the human status.