The karma-yogī who neither hates nor desires the fruits of his activities and tolerates all dualities is a fixed renunciant (nitya-sannyāsī). Easily he is freed from bondage. A sannyāsī is meant to achieve liberation, and one who renounces the fruits of his activities will attain it. Such detachment - feeling neither hatred nor desire for the fruits of work - is the mark of a true sannyāsī. It is not that taking sannyāsa automatically gives liberation.
The pure hearted person engaged in action should be known as nitya-sannyāsī. Because he is completely satisfied with the realization of ātmā contained within karma-yoga, he does not long for, nor does he hate anything at all. By being fixed in karma which is easy to perform, without effort, he is freed from bondage.