Bhashya
कतमे वसव इति तेषां स्वरूपं प्रत्येकं पृच्छयते ; अग्निश्च पृथिवी चेति- अग्न्याद्या नक्षत्रान्ता एते वसवः- प्राणिनां कर्मफलाश्रयत्वेन कार्यकारणसंघातरूपेण तन्निवासत्वेन च विपरिणमन्तः जगदिदं सर्वं वासयन्ति वसन्ति च ; ते यस्माद्वासयन्ति तस्माद्वसव इति ॥
In plain words
‘And which exactly are the Vasus?’ — now each one is being taken up by name. Fire, Earth, and the rest, from Fire down to the stars, these are the Vasus. They turn themselves into the very body and instruments that carry the fruit of a creature's actions, and into the home that body lives in — and in that way they hold this whole world within themselves, even as they themselves live within it. Because they give everything a place to dwell, they are called Vasus.
Close to the Sanskrit
'Which are the Vasus?' — their individual identity is asked about, one by one. 'Fire and Earth, and...' — these, beginning with Fire and ending with the constellations, are the Vasus. Transforming themselves, by being the receptacle of the fruit of action of living beings, into the form of the effect-and-cause aggregate, and by being the dwelling place of that [aggregate], they cause this whole world to dwell [in them] and they dwell [in it]. Since they cause [things] to dwell, therefore they are Vasus.