The word gṛheṣu is significant in this verse. Out of the four āśramas—the brahmacarya, gṛhastha, vānaprastha and sannyāsa—only a gṛhastha, or householder, is allowed to associate with women; therefore the gṛhastha-āśrama is a kind of license for sense gratification given to the devotee. Pṛthu Mahārāja was special in that although he was given license to remain a householder, and although he possessed immense opulences in his kingdom, he never engaged in sense gratification. This was a special sign that indicated him to be a pure devotee of the Lord. A pure devotee is never attracted by sense gratification, and consequently he is liberated. In material life a person engages in sense gratification for his own personal satisfaction, but in the devotional or liberated life one aims to satisfy the senses of the Lord.
In this verse Mahārāja Pṛthu is likened to the sun (arka-vat). Sometimes the sun shines on stool, urine and so many other polluted things, but since the sun is all-powerful, it is never affected by the polluted things with which it associates. On the contrary, the sunshine sterilizes and purifies polluted and dirty places. Similarly, a devotee may engage in so many material activities, but because he has no desire for sense gratification, they never affect him. On the contrary, he dovetails all material activities for the service of the Lord. Since a pure devotee knows how to utilize everything for the Lord's service, he is never affected by material activities. Instead, by his transcendental plans he purifies such activities. This is described in Bhakti-rasāmṛta-sindhu. Sarvopādhi-vinirmuktaṁ tat-paratvena nirmalam: (CC Madhya 19.170) his aim is to become completely purified in the service of the Lord without being affected by material designations.