Effect of Chanting Hare Krishna Mantra
By performing congregational chanting of Hare Krishna mantra, one can destroy the sinful condition of material existence, purify the unclean heart and awaken all varieties of devotional service.
Benefits of Sankirtana
The wild tigers, elephants, bear and deer all together accompanied the Lord, and the Lord accompanied them in sankirtana. By this He proved that by the propagation of the sankirtana movement (congregational chanting and glorifying of the name of the Lord) even the wild animals can live in peace and friendship, and what to speak of men who are supposed to be civilized.
Srimad Bhagavatam Introduction.
Source of Strength
Men become strong and stout by eating sufficient grains, but the devotee who simply eats ordinary grains but does not taste the transcendental pastimes of Lord Chaitanya Mahaprabhu and Krishna gradually becomes weak and falls down from the transcendental position.
Existence of Animalistic Envy
Animalistic envy exists in human society as long as there is no performance of sankirtana-yajna.
Purport on Srimad Bhagavatam on 4.30.35