SB 4.15.4

ayaṁ tu prathamo rājñāṁ
 pumān prathayitā yaśaḥ
pṛthur nāma mahārājo
 bhaviṣyati pṛthu-śravāḥ
Synonyms: 
ayam — this; tu — then; prathamaḥ — the first; rājñām — of kings; pumān — the male; prathayitā — will expand; yaśaḥ — reputation; pṛthuḥ — Mahārāja Pṛthu; nāma — by name; mahā-rājaḥ — the great king; bhaviṣyati — will become; pṛthu-śravāḥ — of wide renown.
Translation: 
Of the two, the male will be able to expand his reputation throughout the world. His name will be Pṛthu. Indeed, he will be the first among kings.
Purport: 

There are different types of incarnations of the Supreme Personality of Godhead. In the śāstras it is said that Garuḍa (the carrier of Lord Viṣṇu) and Lord Śiva and Ananta are all very powerful incarnations of the Brahman feature of the Lord. Similarly, Śacīpati, or Indra, the King of heaven, is an incarnation of the lusty feature of the Lord. Aniruddha is an incarnation of the Lord’s mind. Similarly, King Pṛthu is an incarnation of the ruling force of the Lord. Thus the saintly persons and great sages predicted the future activities of King Pṛthu, who was already explained as a partial incarnation of a plenary expansion of the Lord.