Īśopaniṣad Mantra 17 explained by Bhaktivinoda Ṭhākura

Śrīla Bhaktivinoda Ṭhākura explains these verses in this way: "One should regard a devotee of Kṛṣṇa to be on the right path of the saints, even though such a devotee may seem to be su-durācāra, 'a person of loose character.' One should try to understand the real purport of the word su-durācāra. A conditioned soul has to act for double functions—namely for the maintenance of the body and again for self-realization. Social status, mental development, cleanliness, austerity, nourishment and the struggle for existence are all for the maintenance of the body. The self-realization part of one's activities is executed in one's occupation as a devotee of the Lord, and one performs actions in that connection also. One must perform these two different functions along parallel lines, because a conditioned soul cannot give up the maintenance of his body. The proportion of activities for maintenance of the body decreases, however, in proportion to the increase in devotional service. As long as the proportion of devotional service does not come to the right point, there is a chance for an occasional exhibition of worldliness. But it should be noted that such worldliness cannot continue for long because, by the grace of the Lord, such imperfections will come to an end very shortly. Therefore the path of devotional service is the only right path. If one is on the right path, even an occasional occurrence of worldliness does not hamper one in the advancement of self-realization."

Iso mantra 17 | Bhaktivedanta Vedabase Online - http://bit.ly/1WHLpbo