CC Ādi 17.111
sei puṇye hailāṅ ebe brāhmaṇa-chāoyāla
“In My last birth I was born in the family of cowherd men, and I gave protection to the calves and cows. Because of such pious activities, I have now become the son of a brāhmaṇa.”
The words of Lord Caitanya Mahāprabhu, the greatest authority, herein clearly indicate that one becomes pious simply by keeping cows and protecting them. Unfortunately, people have become such rascals that they do not even care about the words of an authority. People generally consider cowherd men lowly members of society, but herein Caitanya Mahāprabhu confirms that they are so pious that in their next lives they are going to be brāhmaṇas. The caste system has a specific purpose. If this scientific system is followed, human society will get the greatest benefit. Heeding this instruction by the Lord, people should serve cows and calves and in return get ample quantities of milk. There is no loss in serving the cows and calves, but modern human society has become so degraded that instead of giving protection to the cows and serving them, people are killing them. How can they expect peace and prosperity in human society while committing such sinful activities? It is impossible.