Srimad Bhagavatam Canto 04, Chapter 23, Text 30

SB 4.23.30

ittham-bhutanubhavo ’sau
 prthuh sa bhagavattamah
kirtitam tasya caritam
 uddama-caritasya te
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
 
Maitreya continued: The greatest of all devotees, Maharaja Prthu, was very powerful, and his character was liberal, magnificent and magnanimous. Thus I have described him to you as far as possible.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
 
In this verse the word bhagavattamah is very significant, for the word bhagavat is used especially to refer to the Supreme Personality of Godhead, as the word bhagavan, “the Supreme Personality of Godhead,” is derived from the word bhagavat. Sometimes, however, we see that the word bhagavan is used for great personalities like Lord Brahma, Lord Siva and Narada Muni. This is the case with Prthu Maharaja, who is described here as the best of the bhagavans, or the best of the lords. A person can be so addressed only if he is a great personality who exhibits extraordinary and uncommon features or who attains the greatest goal after his disappearance or who knows the difference between knowledge and ignorance. In other words, the word bhagavan should not be used for ordinary persons.
Srimad Bhagavatam Canto 04, Chapter 23, Text 29
Srimad Bhagavatam Canto 04, Chapter 23, Text 31