Chapter 9 · The Royal Secret · Krishna said
Bhagavad Gita 9.21 — Return when merit ends
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 ||
Meaning
Having enjoyed that vast heaven, they return to the mortal world when their merit runs out. Thus, following Vedic rituals for rewards and desiring pleasures, they keep coming and going.