Srimad Bhagavatam Canto 04, Chapter 23, Text 07

SB 4.23.7

titiksur yata-vag danta
urdhva-reta jitanilah
ariradhayisuh krsnam
acarat tapa uttamam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Maharaja Prthu underwent all these severe austerities in order to control his words and his senses, to refrain from discharging his semen and to control the life air within his body. All this he did for the satisfaction of Krsna. He had no other purpose.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
In Kali-yuga the following is recommended:
harer nama harer nama
harer namaiva kevalam
kalau nasty eva nasty eva
nasty eva gatir anyatha
(Brhan-naradiya Purana)
In order to be recognized by Krsna, the Supreme Personality of Godhead, one should chant the holy name of the Lord continuously, twenty-four hours a day. Unfortunate persons who cannot accept this formula prefer to execute some type of pseudomeditation, without accepting the other processes of austerity. The fact is, however, that one must accept either the severe method of austerity described above to become purified or take to the process of devotional service recommended for pleasing the Supreme Lord, Krsna. The person who is Krsna conscious is most intelligent because in Kali-yuga it is not at all possible to undergo such severe austerities. We need only follow great personalities like Lord Caitanya Mahaprabhu. In His Siksastaka, Lord Caitanya Mahaprabhu wrote, param vijayate sri-krsna-sankirtanam: all glories to the holy names of Lord Krsna, which from the very beginning purify the heart and immediately liberate one. Bhava-mahadavagni-nirvapanam. If the real purpose of all yoga is to please Lord Krsna, then this simple bhakti-yoga system recommended for this age is sufficient. It is necessary, however, to engage constantly in the service of the Lord. Although Prthu Maharaja executed his austerities long before the appearance of Lord Krsna on this planet, his purpose was still to please Krsna.
There are many fools who claim that worship of Krsna began only about five thousand years ago, after the appearance of Lord Krsna in India, but this is not a fact. Prthu Maharaja worshiped Krsna millions of years ago, for Prthu happened to be a descendant of the family of Maharaja Dhruva, who reigned for thirty-six thousand years during the Satya-yuga age. Unless his total life span was one hundred thousand years, how could Dhruva Maharaja reign over the world for thirty-six thousand years? The point is that Krsna worship existed at the beginning of creation and has continued to exist throughout Satya-yuga, Treta-yuga and Dvapara-yuga, and now it is continuing in Kali-yuga. As stated in Bhagavad-gita, Krsna appears not only in this millennium of Brahma’s life, but in every millennium. Therefore worship of Krsna is conducted in all millenniums. It is not that Krsna worship began only when Krsna appeared on this planet five thousand years ago. This is a foolish conclusion that is not substantiated by Vedic literatures.
Also of significance in this verse are the words ariradhayisuh krsnam acarat tapa uttamam: Maharaja Prthu underwent severe types of austerities for the express purpose of worshiping Krsna. Krsna is so kind, especially in this age, that He appears in the transcendental vibration of His holy name. As is said in the Narada-pañcaratra, aradhito yadi haris tapasa tatah kim: if Krsna is worshiped, if He is the goal of advancement, there is no need for one to execute severe types of tapasya, because one has already reached his destination. If, after executing all types of tapasya, one cannot reach Krsna, all his tapasya has no value, for without Krsna all austerity is simply wasted labor, srama eva hi kevalam (Bhag. 1.2.8). We should therefore not be discouraged just because we cannot go to the forest and practice severe austerities. Our life is so short that we must strictly adhere to the principles laid down by the Vaisnava acaryas and peacefully execute Krsna consciousness. There is no need to become despondent. Narottama dasa Thakura recommends, anande bala hari, bhaja vrndavana, sri-guru-vaisnava-pade majaiya mana: for a transcendental, blissful life, chant the Hare Krsna mantra, come worship the holy place of Vrndavana, and always engage in the service of the Lord, of the spiritual master and of the Vaisnavas. This Krsna consciousness movement is therefore very safe and easy. We have only to execute the order of the Lord and fully surrender unto Him. We have only to execute the order of the spiritual master, preach Krsna consciousness and follow in the path of the Vaisnavas. The spiritual master represents both Lord Krsna and the Vaisnavas; therefore by following the instructions of the spiritual master and by chanting Hare Krsna, everything will be all right.
Srimad Bhagavatam Canto 04, Chapter 23, Text 06
Srimad Bhagavatam Canto 04, Chapter 23, Text 08