In this way Vasudeva tried to pacify Kaṁsa by good instruction as well as by philosophical discrimination, but Kaṁsa was not to be pacified because his association was demoniac. Because of his demoniac association, he was a demon, although born in a very high royal family. A demon never cares for any good instruction. He is just like a determined thief: one can give him moral instruction, but it will not be effective. Similarly, those who are demoniac or atheistic by nature can hardly assimilate any good instruction, however authorized it may be. That is the difference between demigods and demons. Those who can accept good instruction and try to live their lives in that way are called demigods, and those who are unable to take such good instruction are called demons.
(Krsna Book).

So to become obedient servant and to have no discrimination of sex and food, that means dogs, and they are not human beings. And camel, although he is a big animal, he takes pleasure in eating his own blood. How is that? You will find the camels are very fond of eating thorns. So the thorns they eat, and the thorns cut the tongue, and the blood comes out. It makes a taste, and he is thinking that the thorns are very tasteful. That is camel. Similarly, we are everyone camel because we are enjoying sex. What is this sex? I am spoiling my blood. One drop of semina is created by sixty drops of blood. That is scientific. So when one discharges this semina, he thinks he is enjoying. He does not know that he is spoiling his blood. That is camel. He thinks he is enjoying. He does not think that "I am spoiling my blood. And if I spoil my blood more, then I shall be attacked with so many diseases, I will lose my resistance power." He does not know. But he thinks that sex enjoyment is very nice. It is not nice at all. So therefore dog, hog, camel and ass. What is that ass I have several times given you. The ass means he is working for others for the washerman. So all these businessmen, very busy, but he is working for others, not for himself. He will eat, I suppose, a few slices of bread and a cup of tea or milk; that will satisfy him. But he wants daily one million dollars, and he has to work very hard because a million dollars is not so easy to get. The ass loads on the back tons of clothes of the washerman, and he carries it to the place where they wash, and again carries back. But he is satisfied with a little grass. The ass does not know that "I can get this little grass, there are thousands and thousands of tons of grass on the outer field. Why I am engaged in the service of this washerman and doing this?" He has no sense. He thinks that carrying the tons of clothes for the washerman he has responsibility in business, so many things.
(Lecture on Srimad Bhagavatam--1:3:9--Los Angeles--15th. September, 1972).

True reverential devotion is exhibited by persons who think themselves subordinate to Kṛṣṇa and by persons who think themselves sons of Kṛṣṇa. The best examples of this subordination are Sāraṇa, Gada and Subhadrā. They were all members of the Yadu dynasty, and they always used to think themselves protected by Kṛṣṇa. Similarly, Kṛṣṇa's sons, such as Pradyumna, Cārudeṣṇa and Sāmba, felt the same way. Kṛṣṇa had many sons in Dvārakā. He begot ten sons by each of His 16,108 queens, and all of these sons, headed by Pradyumna, Cārudeṣṇa and Sāmba, used to think themselves always protected by Kṛṣṇa. When Kṛṣṇa's sons dined with Him, they would sometimes open their mouths for Kṛṣṇa to feed them. Sometimes when Kṛṣṇa would pat one of His sons, the son would sit on Kṛṣṇa's lap, and while Kṛṣṇa was blessing the son's head by smelling it, the others would shed tears, thinking how many pious activities he must have performed in his previous life. Out of Kṛṣṇa's many sons, Pradyumna, a son of Kṛṣṇa's chief queen, Rukmiṇī, is considered the leader. Pradyumna's bodily features resemble Kṛṣṇa's exactly. Pure devotees of Kṛṣṇa glorify Pradyumna because he is so fortunate:like father like son.
(Nectar of Devotion).