Shiva Purana
तपस्वी विजिताहारो यमाय योगम भ्यसेत् ॥ यथा दृढतरा बुद्धिरविचाल्या भवेत्तथा ॥ २८ ॥
An ascetic who has conquered his diet should practice yoga for Yama. The more firm and unshakable the intellect becomes.
english translation
tapasvI vijitAhAro yamAya yogama bhyaset ॥ yathA dRDhatarA buddhiravicAlyA bhavettathA ॥ 28 ॥
hk transliteration by Sanscript