Bhagavad Gītā Chapter Four verse 28

द्रव्ययज्ञास्तपोयज्ञा योगयज्ञास्तथापरे ।
स्वाध्यायज्ञानयज्ञाश्च यतयः संशितव्रताः ॥ २८ ॥

dravyayajñās tapoyajñā yogayajñās tathāpare |
svādhyāyajñānayajñāśca yatayaḥ saṃśitavratāḥ ||

dravya - a substance, thing, object; the ingredients or materials of anything; medicinal substance or drugyajña - act of worship or devotion; offering, oblation, sacrificetapas - to heat; religious austerity; self-discipline; pain, sufferingyoga - the act of yoking, joining, attaching, harnessing; a yoke, team, vehicle, conveyance; employment, use, application, performance; a means, expedient, device, way, manner, methodsvādhyāya - to study; to read; sacred recitation; study of the selfjñāna - knowing; knowledge; higher knowledgevrata - vow

Commentaries and Reflections

Commentary by T Krishnamacharya:

Tapas is an offering for something else, not a deprivation.”