SB 11.21.23

phala-śrutir iyaṁ nṝṇāṁ
 na śreyo rocanaṁ param
śreyo-vivakṣayā proktaṁ
 yathā bhaiṣajya-rocanam
Synonyms: 
phala-śrutiḥ — the statements of scripture promising rewards; iyam — these; nṝṇām — for men; na — are not; śreyaḥ — the highest good; rocanam — enticement; param — merely; śreyaḥ — the ultimate good; vivakṣayā — with the idea of saying; proktam — spoken; yathā — just as; bhaiṣajya — for taking medicine; rocanam — inducement.
Translation: 
Those statements of scripture promising fruitive rewards do not prescribe the ultimate good for men but are merely enticements for executing beneficial religious duties, like promises of candy spoken to induce a child to take beneficial medicine.
Purport: 

In the previous verse Lord Kṛṣṇa stated that persons absorbed in sense gratification certainly deviate from the real purpose of human life. But since the Vedas themselves promise heavenly sense gratification as the result of sacrifice and austerity, how can such promotion to heaven be considered a deviation from the goal of life? The Lord here explains that the fruitive rewards offered in religious scriptures are merely inducements, like candy that is used to induce a child to take medicine. It is actually the medicine that is beneficial, and not the candy. Similarly, in fruitive sacrifices it is the worship of Lord Viṣṇu that is beneficial, not the fruitive reward itself. According to Bhagavad-gītā, those professing fruitive rewards to be the ultimate goal of religious scripture are certainly less intelligent fools inimical to the purpose of the Supreme Personality of Godhead. The Lord desires that all conditioned souls be purified and come back home, back to Godhead, for an eternal life of bliss and knowledge. One who opposes the Lord’s purpose in the name of religiosity is certainly bewildered about the purpose of life.