Srimad Bhagavatam Canto 06, Chapter 03, Text 13

SB 6.3.13

yo namabhir vaci janam nijayam
 badhnati tantryam iva damabhir gah
yasmai balim ta ime nama-karma-
 nibandha-baddhas cakita vahanti
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Just as the driver of a bullock cart ties ropes through the nostrils of his bulls to control them, the Supreme Personality of Godhead binds all men through the ropes of His words in the Vedas, which set forth the names and activities of the distinct orders of human society [brahmana, ksatriya, vaisya and sudra]. In fear, the members of these orders all worship the Supreme Lord by offering Him presentations according to their respective activities.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
In this material world, everyone is conditioned, regardless of who he is. One may be a human being, a demigod or an animal, tree or plant, but everything is controlled by the laws of nature, and behind this natural control is the Supreme Personality of Godhead. This is confirmed by Bhagavad-gita (9.10), wherein Krsna says, mayadhyaksena prakrtih suyate sa-caracaram: “The material nature is working under My direction and producing all moving and nonmoving beings.” Thus Krsna is behind the natural machine, which works under His control.
Apart from other living entities, the living being in the human form of body is systematically controlled by the Vedic injunctions in terms of the divisions of varna and asrama. A human being is expected to follow the rules and regulations of varna and asrama; otherwise he cannot escape punishment by Yamaraja. The point is that every human being is expected to elevate himself to the position of a brahmana, the most intelligent man, and then one must transcend that position to become a Vaisnava. This is the perfection of life. The brahmana, ksatriya, vaisya and sudra can elevate themselves by worshiping the Lord according to their activities (sve sve karmany abhiratah samsiddhim labhate narah). The divisions of varna and asrama are necessary to insure the proper execution of duties and peaceful existence for everyone, but everyone is directed to worship the Supreme Lord, who is all-pervading (yena sarvam idam tatam). The Supreme Lord exists vertically and horizontally (otam protam), and therefore if one follows the Vedic injunctions by worshiping the Supreme Lord according to one’s ability, his life will be perfect. As stated in Srimad-Bhagavatam (1.2.13):
atah pumbhir dvija-srestha
svanusthitasya dharmasya
 samsiddhir hari-tosanam
“O best among the twice-born, it is therefore concluded that the highest perfection one can achieve, by discharging his prescribed duties [dharma] according to caste divisions and orders of life, is to please the Lord Hari.” The varnasrama institution offers the perfect process for making one eligible to return home, back to Godhead, because the aim of every varna and asrama is to please the Supreme Lord. One can please the Lord under the direction of a bona fide spiritual master, and if one does so his life is perfect. The Supreme Lord is worshipable, and everyone worships Him directly or indirectly. Those who worship Him directly get the results of liberation quickly, whereas the liberation of those who serve Him indirectly is delayed.
The words namabhir vaci are very important. In the varnasrama institution, there are different names — brahmana, ksatriya, vaisya, sudra, brahmacari, grhastha, vanaprastha and sannyasi. The vak, or Vedic injunctions, give directions for all these divisions. Everyone is expected to offer obeisances to the Supreme Lord and perform duties as indicated in the Vedas.
Srimad Bhagavatam Canto 06, Chapter 03, Text 12
Srimad Bhagavatam Canto 06, Chapter 03, Text 14-15