Bhagavad Gita 17.18
Austerity coupled with hypocrisy, or performed for the sake of self-glorification, popularity, or vanity, comes from passion, and its result is always uncertain and temporary.
सत्कारमानपूजार्थं तपो दम्भेन चैव यत्।क्रियते तदिह प्रोक्तं राजसं चलमध्रुवम्॥satkāramānapūjārthaṃ tapo dambhena caiva yat|kriyate tadiha proktaṃ rājasaṃ calamadhruvam||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).