Bhagavad Gita 9.21 is Chapter 9, Verse 21, in Raja Vidya Raja Guhya Yoga (Royal Knowledge). Below are the Sanskrit text, a transliteration, a plain-English translation and an explanation.
te taṁ bhuktvā svarga-lokaṁ viśālaṁ kṣīṇe puṇye martya-lokaṁ viśanti evaṁ trayī-dharmam anuprapannā gatāgataṁ kāma-kāmā labhante
"Having enjoyed the vast heavenly realm, when their merit is exhausted, they return to the mortal world. Thus following the religious rites of the three Vedas, desiring pleasures, they attain only coming and going."
What This Means:
After enjoying heaven, when the merit runs out (kshine punye), they RETURN to earth. The cycle continues, going up, coming down, going up, coming down. As long as they desire pleasures, they get cycling, not liberation.
Going Deeper:
Heaven is like a vacation, enjoyable but temporary. You return when the money runs out. Those who desire sense pleasures (kama-kama) keep cycling. Liberation requires wanting something beyond pleasure.
How To Apply This:
What do you really want? Pleasure (temporary) or freedom (permanent)? Be honest. There's no shame in wanting pleasure, but recognize it leads to cycling, not completion.
Where this verse sits
Verses 20 and 21 of chapter 9 form one sentence about the followers of the three Vedas, the Rig, Yajur and Sama, who perform sacrifices, drink the soma and pray for heaven. Verse 20 grants that they reach it and enjoy its divine pleasures. Verse 21 gives the second half: they come back. It sets up the contrast of verse 22, where Krishna says of those who worship him with no other thought, 'I carry what they lack and preserve what they have'.
What the words say
Kshine punye, 'when the merit is used up', is the mechanism. Heaven in this picture is not a permanent state but the spending of an account, and when the balance is gone the soul re-enters the mortal world, martya-loka. Gata-agatam, 'going and coming', names the result: not liberation but travel. Trayi-dharma is the religion of the three Vedas, the ritual system whose rewards 2.42 to 2.44 had already called flowery speech. Kama-kamah, 'desirers of desires', gives the cause: as long as pleasure is the aim, pleasure and its expiry are what you get.
A common misreading
The verse is not an attack on the Vedas or on ritual as such; Krishna calls himself the enjoyer of all sacrifices in verse 24 and the goal of the Vedas in 15.15. The criticism is of the aim. Ritual performed to win something is a transaction, and transactions end. The same logic appears in 8.16, where every world up to Brahma's is subject to return. The verse asks the reader to notice what they are actually praying for, because that, and not the form of the prayer, decides whether the result lasts.
Key Sanskrit Terms: