Bg 5.12

yuktah karma-phalam tyaktva
santim apnoti naisthikim
ayuktah kama-karena
phale sakto nibadhyate

Word for word: 
yuktah — one who is engaged in devotional service; karma-phalam — the results of all activities; tyaktva — giving up; santim — perfect peace; apnoti — achieves; naisthikim — unflinching; ayuktah — one who is not in Krishna consciousness; kama-karena — for enjoying the result of work; phale — in the result; saktah — attached; nibadhyate — becomes entangled.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The steadily devoted soul attains unadulterated peace because he offers the result of all activities to Me; whereas a person who is not in union with the Divine, who is greedy for the fruits of his labor, becomes entangled.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The difference between a person in Krishna consciousness and a person in bodily consciousness is that the former is attached to Krishna whereas the latter is attached to the results of his activities. The person who is attached to Krishna and works for Him only is certainly a liberated person, and he has no anxiety over the results of his work. In the Bhagavatam, the cause of anxiety over the result of an activity is explained as being one’s functioning in the conception of duality, that is, without knowledge of the Absolute Truth. Krishna is the Supreme Absolute Truth, the Personality of Godhead. In Krishna consciousness, there is no duality. All that exists is a product of Krishna’s energy, and Krishna is all good. Therefore, activities in Krishna consciousness are on the absolute plane; they are transcendental and have no material effect. One is therefore filled with peace in Krishna consciousness. But one who is entangled in profit calculation for sense gratification cannot have that peace. This is the secret of Krishna consciousness – realization that there is no existence besides Krishna is the platform of peace and fearlessness.