The word kurvanti means "working for others." There is another word, similar to this, which is used when one's activities are done for one's personal sense gratification, but the word kurvanti is used when activities are performed for the satisfaction of the Supreme. Thus in this verse the word can only indicate the rendering of transcendental service to the Lord.
The word hetu means "reason" or "cause." Generally people are engaged in transcendental activities for three reasons: some want material happiness, some want mystic perfection, and some want liberation from material bondage. As far as material enjoyment is concerned, there are so many varieties that no one can enumerate them. As far as perfections in mystic power are concerned, there are eighteen, and as far as types of liberation from material bondage are concerned, there are five. The state of being where all these varieties of enjoyment are conspicuous by their absence is called ahaitukī. The ahaitukī qualification is especially mentioned because by the ahaitukīservice of the Lord, one can achieve the favor of the Lord.