Bhagavad Gita, Chapter 2, Verse 42-44

O Pârtha, no set determination is formed in the minds of those that are deeply attached to pleasure and power, and whose discrimination is stolen away by the flowery words of the unwise, who are full of desires and look upon heaven as their highest goal, and who, taking pleasure in the panegyric words of the Vedas, declare that there is nothing else. Their flowery words are exuberant with various specific rites as the means to pleasure and power, and are the causes of new births as the result of their works performed with desire.

Chasing rewards, even heaven itself, is easy to mistake for the whole point when it was only ever the beginner's version - and a mind that full of wanting has no room left for real resolve.

These verses describe people who read ancient scripture only for the parts that promise comfort, status, and a better rebirth, and stop there. Even a reward as big as heaven is temporary, so building a whole practice around chasing it - a mind constantly calculating what's in it for you - crowds out the kind of steady focus real growth actually needs.