SB 4.23.10
bhagavad-dharminah sadhoh
sraddhaya yatatah sada
bhaktir bhagavati brahmany
ananya-visayabhavat
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Maharaja Prthu thus engaged completely in devotional service, executing the rules and regulations strictly according to principles, twenty-four hours daily. Thus his love and devotion unto the Supreme Personality of Godhead, Krsna, developed and became unflinching and fixed.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The word bhagavad-dharminah indicates that the religious process practiced by Maharaja Prthu was beyond all pretensions. As stated in the beginning of Srimad-Bhagavatam (1.1.2), dharmah projjhita-kaitavo ’tra: religious principles which are simply pretentious are actually nothing but cheating. Bhagavad-dharminah is described by Viraraghava Acarya as nivrtta-dharmena, which indicates that it cannot be contaminated by material aspiration. As described by Srila Rupa Gosvami:
anyabhilasita-sunyam
jñana-karmady-anavrtam
anukulyena krsnanu-
silanam bhaktir uttama
When one who is not inspired by material desires and is not contaminated by the processes of fruitive activity and empiric speculation fully engages in the favorable service of the Lord, his service is called bhagavad-dharma, or pure devotional service. In this verse the word brahmani does not refer to the impersonal Brahman. Impersonal Brahman is a subordinate feature of the Supreme Personality of Godhead, and since impersonal Brahman worshipers desire to merge into the Brahman effulgence, they cannot be considered followers of bhagavad-dharma. After being baffled in his material enjoyment, the impersonalist may desire to merge into the existence of the Lord, but a pure devotee of the Lord has no such desire. Therefore a pure devotee is really bhagavad-dharmi.
It is clear from this verse that Maharaja Prthu was never a worshiper of the impersonal Brahman but was at all times a pure devotee of the Supreme Personality of Godhead. Bhagavati brahmani refers to one who is engaged in devotional service to the Personality of Godhead. A devotee’s knowledge of the impersonal Brahman is automatically revealed, and he is not interested in merging into the impersonal Brahman. Maharaja Prthu’s activities in devotional service enabled him to become fixed and steady in the discharge of devotional activities without having to take recourse to karma, jñana or yoga.