Srimad Bhagavatam Canto 03, Chapter 15, Text 32

SB 3.15.32

munaya ucuh
ko vam ihaitya bhagavat-paricaryayoccais
 tad-dharminam nivasatam visamah svabhavah
tasmin prasanta-puruse gata-vigrahe vam
 ko vatmavat kuhakayoh parisankaniyah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The sages said: Who are these two persons who have developed such a discordant mentality even though they are posted in the service of the Lord in the highest position and are expected to have developed the same qualities as the Lord? How are these two persons living in Vaikuntha? Where is the possibility of an enemy’s coming into this kingdom of God? The Supreme Personality of Godhead has no enemy. Who could be envious of Him? Probably these two persons are imposters; therefore they suspect others to be like themselves.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The difference between the inhabitants of a Vaikuntha planet and those of a material planet is that in Vaikuntha all the residents engage in the service of the Lord Himself and are equipped with all His good qualities. It has been analyzed by great personalities that when a conditioned soul is liberated and becomes a devotee, about seventy-nine percent of all the good qualities of the Lord develop in his person. Therefore in the Vaikuntha world there is no question of enmity between the Lord and the residents. Here in this material world the citizens may be inimical to the chief executives or heads of state, but in Vaikuntha there is no such mentality. One is not allowed to enter Vaikuntha unless he has completely developed the good qualities. The basic principle of goodness is to accept subordination to the Supreme Personality of Godhead. The sages, therefore, were surprised to see that the two doormen who checked them from entering the palace were not exactly like the residents of Vaikunthaloka. It may be said that a doorman’s duty is to determine who should be allowed to enter the palace and who should not. But that is not relevant in this matter because no one is allowed to enter the Vaikuntha planets unless he has developed one hundred percent his mentality of devotional service to the Supreme Lord. No enemy of the Lord can enter Vaikunthaloka. The Kumaras concluded that the only reason for the doormen’s checking them was that the doormen themselves were imposters.
Srimad Bhagavatam Canto 03, Chapter 15, Text 31
Srimad Bhagavatam Canto 03, Chapter 15, Text 33