Bhagavad Gītā Chapter Six verse 46
tapasvibhyo ’dhiko yogī jñānibhyo ’pi mato ’dhikaḥ |
karmibhyaś cādhiko yogī tasmād yogī bhavārjuna ||
Commentaries and Reflections
Commentary by T Krishnamacharya:
Tapas is Proper Diet, Mantra Chanting and Self-Inquiry.