|Chapter 3: Karma-yoga|
ya aste manasa smaran
mithyacarah sa ucyate
One who restrains the senses of action but whose mind dwells on sense objects certainly deludes himself and is called a pretender.
If such a person renounces prescribed duties and accepts sannyasa, though his heart is still not purified, he will find himself in difficulty. Krishna in this verse describes such an unfortunate renunciant. Srila Prabhupada comments, "There are many pretenders who refuse to work in Krishna consciousness but make a show of meditation, while actually dwelling within the mind upon sense enjoyment. Such pretenders may also speak on dry philosophy in order to bluff sophisticated followers, but according to this verse these are the greatest cheaters. For sense enjoyment one can act in any capacity of the social order, but if one follows the rules and regulations of his particular status, he can make gradual progress in purifying his existence. But he who makes a show of being a yogi while actually searching for the objects of sense gratification must be called the greatest cheater, even though he sometimes speaks of philosophy. His knowledge has no value, because the effects of such a sinful man's knowledge are taken away by the illusory energy of the Lord. Such a pretender's mind is always impure, and therefore his show of yogic meditation has no value whatsoever."
Please read the Sanskrit Verse and the Prabhupada's Purport.