Srimad Bhagavatam Canto 09, Chapter 02, Text 17

SB 9.2.17

dhrstad dharstam abhut ksatram
 brahma-bhuyam gatam ksitau
nrgasya vamsah sumatir
 bhutajyotis tato vasuh
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
From the son of Manu named Dhrsta came a ksatriya caste called Dharsta, whose members achieved the position of brahmanas in this world. Then, from the son of Manu named Nrga came Sumati. From Sumati came Bhutajyoti, and from Bhutajyoti came Vasu.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Here it is said, ksatram brahma-bhuyam gatam ksitau: although the Dharstas belonged to the ksatriya caste, they were able to convert themselves into brahmanas. This gives clear evidence supporting the following statement by Narada (Bhag. 7.11.35):
 
yasya yal laksanam proktam
 pumso varnabhivyañjakam
yad anyatrapi drsyeta
 tat tenaiva vinirdiset
 
If the qualities of one group are found in the men of another, those men should be recognized by their qualities, by their symptoms, not by the caste of the family in which they were born. Birth is not at all important; it is one’s qualities that are stressed in all Vedic literature.
Srimad Bhagavatam Canto 09, Chapter 02, Text 16
Srimad Bhagavatam Canto 09, Chapter 02, Text 18