Bg 5.2

sri-bhagavan uvaca
sannyasah karma-yogas ca
nihsreyasa-karav ubhau
tayos tu karma-sannyasat
karma-yogo visisyate

Word for word: 
sri-bhagavan uvaca — the Personality of Godhead said; sannyasah — renunciation of work; karma-yogah — work in devotion; ca — also; nihsreyasa-karau — leading to the path of liberation; ubhau — both; tayoh — of the two; tu — but; karma-sannyasat — in comparison to the renunciation of fruitive work; karma-yogah — work in devotion; visisyate — is better.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Personality of Godhead replied: The renunciation of work and work in devotion are both good for liberation. But, of the two, work in devotional service is better than renunciation of work.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Fruitive activities (seeking sense gratification) are cause for material bondage. As long as one is engaged in activities aimed at improving the standard of bodily comfort, one is sure to transmigrate to different types of bodies, thereby continuing material bondage perpetually. Srimad-Bhagavatam (5.5.4–6) confirms this as follows:

nunam pramattah kurute vikarma
yad indriya-pritaya aprnoti
na sadhu manye yata atmano ’yam
asann api klesa-da asa dehah

parabhavas tavad abodha-jato
yavan na jijnasata atma-tattvam
yavat kriyas tavad idam mano vai
karmatmakam yena sarira-bandhah

evam manah karma-vasam prayunkte
avidyayatmany upadhiyamane
pritir na yavan mayi vasudeve
na mucyate deha-yogena tavat

“People are mad after sense gratification, and they do not know that this present body, which is full of miseries, is a result of one’s fruitive activities in the past. Although this body is temporary, it is always giving one trouble in many ways. Therefore, to act for sense gratification is not good. One is considered to be a failure in life as long as he makes no inquiry about his real identity. As long as he does not know his real identity, he has to work for fruitive results for sense gratification, and as long as one is engrossed in the consciousness of sense gratification one has to transmigrate from one body to another. Although the mind may be engrossed in fruitive activities and influenced by ignorance, one must develop a love for devotional service to Vasudeva. Only then can one have the opportunity to get out of the bondage of material existence.”

Therefore, jnana (or knowledge that one is not this material body but spirit soul) is not sufficient for liberation. One has to act in the status of spirit soul, otherwise there is no escape from material bondage. Action in Krishna consciousness is not, however, action on the fruitive platform. Activities performed in full knowledge strengthen one’s advancement in real knowledge. Without Krishna consciousness, mere renunciation of fruitive activities does not actually purify the heart of a conditioned soul. As long as the heart is not purified, one has to work on the fruitive platform. But action in Krishna consciousness automatically helps one escape the result of fruitive action so that one need not descend to the material platform. Therefore action in Krishna consciousness is always superior to renunciation, which always entails a risk of falling. Renunciation without Krishna consciousness is incomplete, as is confirmed by Srila Rupa Gosvami in his Bhakti-rasamrta-sindhu (1.2.258):

prapancikataya buddhya
hari-sambandhi-vastunah
mumuksubhih parityago
vairagyam phalgu kathyate

“When persons eager to achieve liberation renounce things related to the Supreme Personality of Godhead, thinking them to be material, their renunciation is called incomplete.” Renunciation is complete when it is in the knowledge that everything in existence belongs to the Lord and that no one should claim proprietorship over anything. One should understand that, factually, nothing belongs to anyone. Then where is the question of renunciation? One who knows that everything is Krishna’s property is always situated in renunciation. Since everything belongs to Krishna, everything should be employed in the service of Krishna. This perfect form of action in Krishna consciousness is far better than any amount of artificial renunciation by a sannyasi of the Mayavadi school.