Bhagavad Gītā Chapter Six verse 46

तपस्विभ्योऽधिको योगी ज्ञानिभ्योऽपि मतोऽधिक: ।
कर्मिभ्यश्चाधिको योगी तस्माद्योगी भवार्जुन ॥ ४६ ॥

tapasvibhyo ’dhiko yogī jñānibhyo ’pi mato ’dhikaḥ |
karmibhyaś cādhiko yogī tasmād yogī bhavārjuna ||

tapas - to heat; religious austerity; self-discipline; pain, suffering

Commentaries and Reflections

Commentary by T Krishnamacharya:

Tapas is Proper Diet, Mantra Chanting and Self-Inquiry.”