Ksatriya kings used to obey very faithfully the orders of learned brahmanas and saintly persons, and in this way they would rule their country. Similarly, vaisyas used to follow the king's orders, and sudras used to serve the three higher castes

Expressions researched:
"Ksatriya kings used to obey very faithfully the orders of learned brahmanas and saintly persons, and in this way they would rule their country. Similarly, vaisyas used to follow the king's orders, and sudras used to serve the three higher castes"

CC Madhya-lila

Sārvabhauma Bhaṭṭācārya was a brāhmaṇa and a realized soul, whereas Pratāparudra was a kṣatriya. Kṣatriya kings used to obey very faithfully the orders of learned brāhmaṇas and saintly persons, and in this way they would rule their country. Similarly, vaiśyas used to follow the king's orders, and śūdras used to serve the three higher castes.

CC Madhya 10.17, Translation and Purport:

The King said, “Bhaṭṭācārya, you are the most learned and experienced person I know. Therefore when you address Śrī Caitanya Mahāprabhu as Lord Kṛṣṇa, I accept this as the truth.

This is the way to advance in spiritual science. One must accept the words of an ācārya, a bona fide spiritual master, to clear the path for spiritual advancement. This is the secret of success. However, one's guide must be a spiritual master who is actually an unalloyed devotee strictly following the instructions of the previous ācārya without deviation. Whatever the spiritual master says must be accepted by the disciple. Only then is success certain. This is the Vedic system.

Sārvabhauma Bhaṭṭācārya was a brāhmaṇa and a realized soul, whereas Pratāparudra was a kṣatriya. Kṣatriya kings used to obey very faithfully the orders of learned brāhmaṇas and saintly persons, and in this way they would rule their country. Similarly, vaiśyas used to follow the king's orders, and śūdras used to serve the three higher castes. In this way the brāhmaṇas, kṣatriyas, vaiśyas and śūdras used to live cooperatively, performing their respective duties. Consequently society was peaceful, and people were able to discharge the duties of Kṛṣṇa consciousness. Thus they were happy in this life and able to return home, back to Godhead.