SB 10.2.34

As stated in Bhagavad-gītā (18.3), yajña-dāna-tapaḥ-karma na tyājyam: the Vedic ritualistic ceremonies, charity, austerity and all such prescribed duties are never to be given up. Yajño dānaṁ tapaś caiva pāvanāni manīṣiṇām (18.5): even one who is very much advanced in spiritual realization must still execute the Vedic principles. Even in the lowest stage, the karmīs are advised to work for the sake of the Lord.

yajñārthāt karmaṇo ’nyatra
loko ’yaṁ karma-bandhanaḥ
“Work done as a sacrifice for Viṣṇu has to be performed, otherwise work binds one to this material world.” (Bg. 3.9) The words yajñārthāt karmaṇaḥ indicate that while performing all kinds of duties, one should remember that these duties should be performed to satisfy the Supreme Lord (sva-karmaṇā tam abhyarcya). According to Vedic principles, there must be divisions of human society (cātur-varṇyaṁ mayā sṛṣṭam). There should be brāhmaṇas, kṣatriyas, vaiśyas and śūdras, and everyone should learn to worship the Supreme Personality of Godhead (tam abhyarcya). This is real human society, and without this system we are left with animal society.

The modern activities of human society are described in Śrīmad-Bhāgavatam as the activities of go-khara, cows and asses (sa eva go-kharaḥ). Everyone is acting in a bodily concept of life involving society, friendship and love for the improvement of economic and political conditions, and thus all activities are enacted in ignorance. The Supreme Personality therefore comes to teach us how to act according to the Vedic principles. In this Age of Kali, the Supreme Personality of Godhead appeared as Śrī Caitanya Mahāprabhu and preached that in this age the Vedic activities cannot be systematically performed because people are so fallen. He gave this recommendation from the śāstras:

harer nāma harer nāma
harer nāmaiva kevalam
kalau nāsty eva nāsty eva
nāsty eva gatir anyathā
“In this age of quarrel and hypocrisy the only means of deliverance is chanting the holy name of the Lord. There is no other way. There is no other way. There is no other way.” The Kṛṣṇa consciousness movement is therefore teaching people all over the world how to chant the Hare Kṛṣṇa mantra, and this has proved very much effective in all places at all times. The Supreme Personality of Godhead appears in order to teach us Vedic principles intended for understanding Him (vedaiś ca sarvair aham eva vedyaḥ). We should always know that when Kṛṣṇa and Lord Caitanya appeared, They appeared in śuddha-sattva bodies. One should not mistake the body of Kṛṣṇa or Caitanya Mahāprabhu to be a material body like ours, for Kṛṣṇa and Caitanya Mahāprabhu appeared as needed for the benefit of the entire human society. Out of causeless mercy, the Lord appears in different ages in His original śuddha-sattva transcendental body to elevate human society to the spiritual platform upon which they can truly benefit. Unfortunately, modern politicians and other leaders stress the bodily comforts of life (yasyātma-buddhiḥ kuṇape tri-dhātuke) and concentrate on the activities of this ism and that ism, which they describe in different kinds of flowery language. Essentially such activities are the activities of animals (sa eva go-kharaḥ). We should learn how to act from Bhagavad-gītā, which explains everything for human understanding. Thus we can become happy even in this Age of Kali.