Srimad Bhagavatam Canto 06, Chapter 09, Text 50

SB 6.9.50

svayam nihsreyasam vidvan
 na vakty ajñaya karma hi
na rati rogino ’pathyam
 vañchato ’pi bhisaktamah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
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.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
Here is the difference between the benedictions awarded by the demigods and those awarded by the Supreme Personality of Godhead, Visnu. Devotees of the demigods ask for benedictions simply for sense gratification, and therefore they have been described in Bhagavad-gita (7.20) as bereft of intelligence.
kamais tais tair hrta-jñanah
 prapadyante ’nya-devatah
tam tam niyamam asthaya
 prakrtya niyatah svaya
“Those whose minds are distorted by material desires surrender unto demigods and follow the particular rules and regulations of worship according to their own natures.”
Conditioned souls are generally bereft of intelligence because of profound desires for sense gratification. They do not know what benedictions to ask. Therefore nondevotees are advised in the sastras to worship various demigods to achieve material benefits. For example, if one wants a beautiful wife, he is advised to worship Uma, or the goddess Durga. If one wants to be cured of a disease, he is advised to worship the sun-god. All requests for benedictions from the demigods, however, are due to material lust. The benedictions will be finished at the end of the cosmic manifestation, along with those who bestow them. If one approaches Lord Visnu for benedictions, the Lord will give him a benediction that will help him return home, back to Godhead. This is also confirmed by the Lord Himself in Bhagavad-gita (10.10):
tesam satata-yuktanam
 bhajatam priti-purvakam
dadami buddhi-yogam tam
 yena mam upayanti te
Lord Visnu, or Lord Krsna, instructs a devotee who constantly engages in His service how to approach Him at the end of his material body. The Lord says in Bhagavad-gita (4.9):
janma karma ca me divyam
 evam yo vetti tattvatah
tyaktva deham punar janma
 naiti mam eti so ’rjuna
“One who knows the transcendental nature of My appearance and activities, does not, upon leaving the body, take his birth again in this material world, but attains My eternal abode, O Arjuna.” This is the benediction of Lord Visnu, Krsna. After giving up his body, a devotee returns home, back to Godhead.
A devotee may foolishly ask for material benedictions, but Lord Krsna does not give him such benedictions, despite the devotee’s prayers. Therefore people who are very attached to material life do not generally become devotees of Krsna or Visnu. Instead they become devotees of the demigods (kamais tais tair hrta jñanah prapadyante ’nya-devatah). The benedictions of the demigods, however, are condemned in Bhagavad-gita. Antavat tu phalam tesam tad bhavaty alpa-medhasam: “Men of small intelligence worship the demigods, and their fruits are limited and temporary.” A non-Vaisnava, one who is not engaged in the service of the Supreme Personality of Godhead, is considered a fool with a small quantity of brain substance.
Srimad Bhagavatam Canto 06, Chapter 09, Text 49
Srimad Bhagavatam Canto 06, Chapter 09, Text 51