Bhagavad Gita Chapter 03, Text 19

Bg 3.19

tasmad asaktah satatam
karyam karma samacara
asakto hy acaran karma
param apnoti purusah

Word for word: 
tasmat — therefore; asaktah — without attachment; satatam — constantly; karyam — as duty; karma — work; samacara — perform; asaktah — unattached; hi — certainly; acaran — performing; karma — work; param — the Supreme; apnoti — achieves; purusah — a man.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Therefore, without being attached to the fruits of activities, one should act as a matter of duty, for by working without attachment one attains the Supreme.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Supreme is the Personality of Godhead for the devotees, and liberation for the impersonalist. A person, therefore, acting for Krishna, or in Krishna consciousness, under proper guidance and without attachment to the result of the work, is certainly making progress toward the supreme goal of life. Arjuna is told that he should fight in the Battle of Kuruksetra for the interest of Krishna because Krishna wanted him to fight. To be a good man or a nonviolent man is a personal attachment, but to act on behalf of the Supreme is to act without attachment for the result. That is perfect action of the highest degree, recommended by the Supreme Personality of Godhead, Sri Krishna.

Vedic rituals, like prescribed sacrifices, are performed for purification of impious activities that were performed in the field of sense gratification. But action in Krishna consciousness is transcendental to the reactions of good or evil work. A Krishna conscious person has no attachment for the result but acts on behalf of Krishna alone. He engages in all kinds of activities, but is completely nonattached.