Bhagavad Gita, Chapter 9, Verse 21

ते तं भुक्त्वा स्वर्गलोकं विशालं क्षीणे पुण्ये मर्त्यलोकं विशन्ति । एवं त्रयीधर्ममनुप्रपन्ना गतागतं कामकामा लभन्ते

te taṃ bhuktvā svargalokaṃ viśālaṃ kṣīṇe puṇye martyalokaṃ viśanti | evaṃ trayīdharmamanuprapannā gatāgataṃ kāmakāmā labhante

Translation

They, having enjoyed that spacious world of Svarga, their merit (puṇya) exhausted, enter the world of the mortals; thus following the Dharma of the Triad, desiring (objects of) desires, they attain to the state of going and returning.

— Alladi Mahadeva Sastri

Word meanings

te

they

tam

that

bhuktvā

having enjoyed

svargalokam

svarga-world

viśālam

vast

kṣīṇe

(in the state of being) withered

puṇye

(in) merit

martyalokam

of mortals, the world

viśanti

enter

evam

thus

trayīdharmam

of the three (Vedas), the duty

anuprapannāḥ

devoted (to)

gatāgatam

going, and, coming, and

kāmakāmāḥ

of (objects of) desire, desire, whose, they

labhante

obtain

Śaṅkarācārya's commentary

The Dharma of the Triad: mere Vedic ritual (karma) that which is enjoined by the three Vedas. They have to go and return, and never attain independence anywhere.