sa ittham bhakti-yogena
sva-dharmena harim prinan
sarvan kaman sanair jahau
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The king of this planet, Maharaja Ambarisa, thus performed devotional service to the Lord and in this endeavor practiced severe austerity. Always satisfying the Supreme Personality of Godhead by his constitutional activities, he gradually gave up all material desires.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Severe austerities in the practice of devotional service are of many varieties. For example, in worshiping the Deity in the temple there are certainly laborious activities. Sri-vigraharadhana-nitya-nana-srngara-tan-mandira-marjanadau. One must decorate the Deity, cleanse the temple, bring water from the Ganges and Yamuna, continue the routine work, perform arati many times, prepare first-class food for the Deity, prepare dresses and so on. In this way, one must constantly be engaged in various activities, and the hard labor involved is certainly an austerity. Similarly, the hard labor involved in preaching, preparing literature, preaching to atheistic men and distributing literature door to door is of course an austerity (tapo-yuktena). Tapo divyam putraka. Such austerity is necessary. Yena sattvam suddhyet. By such austerity in devotional service, one is purified of material existence (kaman sanair jahau). Indeed, such austerity leads one to the constitutional position of devotional service. In this way one can give up material desires, and as soon as one is freed from material desires, he is free from the repetition of birth and death, old age and disease.