SB 4.22.49
vainyas tu dhuryo mahatam
samsthityadhyatma-siksaya
apta-kamam ivatmanam
mena atmany avasthitah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Amongst great personalities, Maharaja Prthu was the chief by virtue of his fixed position in relation to spiritual enlightenment. He remained satisfied as one who has achieved all success in spiritual understanding.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Remaining fixed in devotional service gives one the utmost in self-satisfaction. Actually self-satisfaction can be achieved only by pure devotees, who have no desire other than to serve the Supreme Personality of Godhead. Since the Supreme Personality of Godhead has nothing to desire, He is fully satisfied with Himself. Similarly, a devotee who has no desire other than to serve the Supreme Personality of Godhead is as self-satisfied as the Supreme Lord. Everyone is hankering after peace of mind and self-satisfaction, but these can only be achieved by becoming a pure devotee of the Lord.
King Prthu’s statements in previous verses regarding his vast knowledge and perfect devotional service are justified here, for he is considered best amongst all mahatmas. In Bhagavad-gita (9.13) Sri Krsna speaks of mahatmas in this way:
mahatmanas tu mam partha
daivim prakrtim asritah
bhajanty ananya-manaso
jñatva bhutadim avyayam
“O son of Prtha, those who are not deluded, the great souls, are under the protection of the divine nature. They are fully engaged in devotional service because they know Me as the Supreme Personality of Godhead, original and inexhaustible.”
The mahatmas are not under the clutches of the illusory energy but are under the protection of the spiritual energy. Because of this, the real mahatma is always engaged in the devotional service of the Lord. Prthu Maharaja exhibited all the symptoms of a mahatma; therefore he is mentioned in this verse as dhuryo mahatam, best of the mahatmas.