Srimad Bhagavatam Canto 10, Chapter 01, Text 64

SB 10.1.64

etat kamsaya bhagavañ
 chasamsabhyetya naradah
bhumer bharayamananam
 daityanam ca vadhodyamam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Once the great saint Narada approached Kamsa and informed him of how the demoniac persons who were a great burden on the earth were going to be killed. Thus Kamsa was placed into great fear and doubt.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
It has already been discussed that mother earth implored Lord Brahma to give her relief from the distress created by the burdensome demons and that Lord Brahma informed her that Lord Krsna Himself was going to appear. Krsna says in Bhagavad-gita (4.8):
paritranaya sadhunam
 vinasaya ca duskrtam
 sambhavami yuge yuge
Whenever there is a burden created by the demons and whenever the innocent devotees are distressed by demoniac rulers, the Lord appears in due course of time to kill the demons with the assistance of His real representatives, who are technically called demigods. In the Upanisads it is stated that the demigods are different parts of the Supreme Personality of Godhead. As it is the duty of the parts of the body to serve the whole, it is the duty of Krsna’s devotees to serve Krsna as He wants. Krsna’s business is to kill the demons, and therefore this should be a devotee’s business also. Because the people of Kali-yuga are fallen, however, Sri Caitanya Mahaprabhu, out of kindness for them, did not bring any weapon to kill them. Rather, by spreading Krsna consciousness, love of Krsna, He wanted to kill their nefarious, demoniac activities. This is the purpose of the Krsna consciousness movement. Unless the demoniac activities on the surface of the world are diminished or vanquished, no one can be happy. The program for the conditioned soul is fully described in Bhagavad-gita, and one simply has to follow these instructions to become happy. Sri Caitanya Mahaprabhu has therefore prescribed:
harer nama harer nama
 harer namaiva kevalam
kalau nasty eva nasty eva
 nasty eva gatir anyatha
Let people chant the Hare Krsna mantra constantly. Then their demoniac tendencies will be killed, and they will become first-class devotees, happy in this life and in the next.
Srimad Bhagavatam Canto 10, Chapter 01, Text 62-63
Srimad Bhagavatam Canto 10, Chapter 01, Text 65-66