yo brahma ksatram avisya
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Dear lord, you are situated in your pure existential position of goodness; therefore you are the perfect representative of the Supreme Lord. You are glorified by your own prowess, and thus you are maintaining the entire world by introducing brahminical culture and protecting everyone in your line of duty as a ksatriya.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Without the spread of brahminical culture and without proper protection from the government, no social standard can be maintained properly. This is admitted in this verse by the citizens of Maharaja Prthu, who could maintain the wonderful situation of his government due to his position in pure goodness. The word vivrddha-sattvaya is significant. In the material world there are three qualities, namely goodness, passion and ignorance. One has to be raised from the platform of ignorance to the platform of goodness by devotional service. There is no other means for elevating one from the lowest stage of life to the highest stage but the execution of devotional service; as advised in the previous chapters of Srimad-Bhagavatam, one can raise himself from the lowest position to the highest simply by associating with devotees and hearing Srimad-Bhagavatam regularly from their mouths:
srnvatam sva-kathah krsnah
hrdy antah-stho hy abhadrani
vidhunoti suhrt satam
“When one engages in devotional service in the first stages of hearing and chanting, the Lord, who is in everyone’s heart, helps the devotee in cleansing his heart.” (Bhag. 1.2.17) In the gradual cleansing process, one is relieved of the influence of passion and ignorance and is situated on the platform of goodness. The result of association with the qualities of passion and ignorance is that one becomes lusty and greedy. But when one is elevated to the platform of goodness, he is satisfied in any condition of life and is without lust and greed. This mentality indicates one’s situation on the platform of goodness. One has to transcend this goodness and raise himself to the pure goodness called vivrddha-sattva, or the advanced stage of goodness. In the advanced stage of goodness one can become Krsna conscious. Therefore Maharaja Prthu is addressed here as vivrddha-sattva, or one who is situated in the transcendental position. But Maharaja Prthu, although situated in the transcendental position of a pure devotee, came down to the position of brahmana and ksatriya for the benefit of human society and thus gave protection to the entire world by his personal prowess. Although he was a king, a ksatriya, because he was a Vaisnava he was also a brahmana. As a brahmana he could give proper instruction to the citizens, and as a ksatriya he could rightly give protection to all of them. Thus the citizens of Maharaja Prthu were protected in all respects by the perfect king.
Thus end the Bhaktivedanta purports of the Fourth Canto, Twenty-first Chapter, of the Srimad-Bhagavatam, entitled “Instructions by Maharaja Prthu.”