Maharaj Prthu, the 9th Incarnation

Verse 1.3.14: We are discussing the different incarnations of the Supreme Personality of Godhead. We are talking about the 9th incarnation, where the Lord descended as a ksatriya. Here Srila Prabhupada is highlighting us about the varnaashrama system. The intelligent class of men (the brahmanas) are responsible for selecting or dethroning the King (the administrative class), according to the rules and regulations of scriptures. If the King is not pious and does not take care of the all-around welfare of his citizens, then they can dethrone him. But they themselves do not occupy this position, as their duty is to simply select a Ksatriya for this purpose, who would fulfill his duties for the welfare of the citizens.

Maharaj Prthu, the ninth incarnation of the Lord is the example being quoted in this verse.