The various actions we perform in this world beget various specific results. When we begin to enjoy these results- the fruits of our work- these actions of enjoyment also produce, in their turn, further results as a matter of course. Thus we develop a big tree of actions and reactions with their respective fruits. And as the enjoyers of these fruits, we become bound up in the network of the tree of work and its fruit. Birth after birth, the spirit soul remains bound up in the process of producing such fruits and enjoying the same. We have very little chance of escaping this bondage of action and reaction- work and its fruitive results. Even after abdicating all work and accepting the life of a sannyasi, or renunciant, one still has to work, if only to fill his hungry stomach. So there is no way out- no way to avoid doing work- if only for the belly’s sake.
So, to solve this dilemma, the Personality of Godhead, Sri Kṛṣṇa, advises us as follows: “The best policy for doing work is to perform all prescribed duties for the satisfaction of Yajna, or Viṣṇu, the Supreme Being and Absolute Truth. Otherwise, all actions will produce reactions that will cause bondage. If work is done for the sake of Yajna, one will become free from all bondage.” This method of work, which does not cause any bondage, is called work with transcendental results, or karma-yoga. By working this way, one not only becomes immune to the bondage of work, but one also develops transcendental devotion toward the Absolute Personality of Godhead. Rather than enjoying the fruits of his work himself, a person should dedicate the same for the transcendental loving service of the Absolute Personality of Godhead.
Source: A.C. Bhaktivedanta Swami Prabhupada (2012 edition), “Message of Godhead”, Page 29