तद्व्यक्षरत्तदादित्यमभितोऽश्रयत्तद्वा एतद्यदेतदादित्यस्य कृष्णंरूपम् ॥ ३.३.३ ॥
In plain words
It flowed forth and settled about the sun; and that is what is the dark form of the sun.
The commentators
Chāndogyopaniṣadbhāṣyam· bhāṣya
अथ येऽस्य प्रत्यञ्चो रश्मय इत्यादि समानम् । तथा साम्ना मधु, एतदादित्यस्य कृष्ण रूपम् ॥
In plain words
Now, the explanation regarding the western rays of the sun is the same as before. Similarly, with regard to the sāman as honey, this constitutes the dark form of the sun.
Close to the Sanskrit
Now, those rays of this [sun] which are westward and so on is the same. Similarly, the honey by the sāman; this is the dark form of the sun.