Canto 6 Chapter 9 Text 50

svayaṁ niḥśreyasaṁ vidvān
na vakty ajñāya karma hi
na rāti rogiṇo ’pathyaṁ
vāñchato ’pi bhiṣaktamaḥ

TRANSLATION
A pure devotee who is fully accomplished in the science of devotional service will never instruct a foolish person to engage in fruitive activities for material enjoyment, not to speak of helping him in such activities. Such a devotee is like an experienced physician, who never encourages a patient to eat food injurious to his health, even if the patient desires it.