Bhagavad Gita Chapter 9, Verse 21

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

te taṁ bhuktvā svarga-lokaṁ viśālaṁ kṣīṇe puṇye martya-lokaṁ viśanti evaṁ trayī-dharmam anuprapannā gatāgataṁ kāmakāmā labhante

After enjoying the vast heavenly world, when their merit is exhausted, they return to the mortal world. Thus, those who follow the path of the three Vedas, desiring pleasures, come and go repeatedly.

Krishna reveals the limitation of seeking heavenly rewards: 'Te tam bhuktvā svarga-lokam viśālam kṣīṇe puṇye martya-lokam viśanti'—they (te), having enjoyed (bhuktvā) that vast (viśālam) heavenly world (svarga-lokam), when their merit is exhausted (kṣīṇe puṇye), return (viśanti) to the mortal world (martya-lokam). 'Evaṁ trayī-dharmam anuprapannā gatāgatam kāmakāmā labhante'—thus (evam), those who follow (anuprapannāḥ) the path of the three Vedas (trayī-dharmam), desiring pleasures (kāmakāmāḥ), obtain (labhante) coming and going (gatāgatam). This is the cycle of material worship: enjoy heavenly pleasures, exhaust merit, return to mortal world. The cycle repeats—coming and going, never ending. This is the limitation of seeking temporary rewards: you get what you seek, but it's temporary. You return to the cycle, never free. This is why devotion is superior: it leads to liberation, not temporary pleasures.