Having enjoyed that vast world of heaven, they enter the world of mortals when their merit runs out. In this way, those who follow the dharma of the three Vedas, longing for pleasures, gain only this coming and going.
Explanation
Krishna continues from the previous verse, describing people who perform Vedic rituals to reach heaven. Their reward lasts only as long as their merit (puṇya), so once it is used up they return to the human world. Krishna's point is that actions done out of desire (kāma) keep a person in the cycle of coming and going, rather than bringing lasting freedom.