Madhvaon Brahma Sūtra 1.3.35

And (besides the reason already given), from the subsequent sentence,4 this is-a chariot (drawn by) .the mule,’ which mentions 4 Chitraratha ’ connected with the king (as its owner) as a characteristic of Poutrayana, Poutrayana is understood to be a Kshatriya (and not a Sudra). The Brabmapurana says: The chariot to which a mule is yoked is called Chitra (i.e., Chitra Ratlia). Further the Brahmavaivarta purana says, “ Where there is (the study of) scripture, there only is the chariot; and where there is ho study of scripture, there no chariot is (to be seen). (A chariot was to be kept by one of the first three classes who alone are fit to study scripture, aud those who are prohibited from •studying scripture are also prohibited from having a chariot).