Srimad Bhagavatam Canto 06, Chapter 01, Text 38

SB 6.1.38

sri-visnuduta ucuh
yuyam vai dharma-rajasya
 yadi nirdesa-karinah
bruta dharmasya nas tattvam
 yac cadharmasya laksanam
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
The blessed messengers of Lord Visnu, the Visnudutas, said: If you are actually servants of Yamaraja, you must explain to us the meaning of religious principles and the symptoms of irreligion.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
This inquiry by the Visnudutas to the Yamadutas is most important. A servant must know the instructions of his master. The servants of Yamaraja claimed to be carrying out his orders, and therefore the Visnudutas very intelligently asked them to explain the symptoms of religious and irreligious principles. A Vaisnava knows these principles perfectly well because he is well acquainted with the instructions of the Supreme Personality of Godhead. The Supreme Lord says, sarva-dharman parityajya mam ekam saranam vraja: “Give up all other varieties of religion and just surrender unto Me.” Therefore surrender unto the Supreme Personality of Godhead is the actual principle of religion. Those who have surrendered to the principles of material nature instead of to Krsna are all impious, regardless of their material position. Unaware of the principles of religion, they do not surrender to Krsna, and therefore they are considered sinful rascals, the lowest of men, and fools bereft of all knowledge. As Krsna says in Bhagavad-gita (7.15):
 
na mam duskrtino mudhah
 prapadyante naradhamah
mayayapahrta-jñana
 asuram bhavam asritah
 
“Those miscreants who are grossly foolish, lowest among mankind, whose knowledge is stolen by illusion, and who partake of the atheistic nature of demons, do not surrender unto Me.” One who has not surrendered to Krsna does not know the true principle of religion; otherwise he would have surrendered.
 
The question posed by the Visnudutas was very suitable. One who represents someone else must fully know that person’s mission. The devotees in the Krsna consciousness movement must therefore be fully aware of the mission of Krsna and Lord Caitanya; otherwise they will be considered foolish. All devotees, especially preachers, must know the philosophy of Krsna consciousness so as not to be embarrassed and insulted when they preach.
Srimad Bhagavatam Canto 06, Chapter 01, Text 37
Srimad Bhagavatam Canto 06, Chapter 01, Text 39