8.21 अव्यक्तः unmanifested, अक्षरः imperishable, इति thus, उक्तः called, तम् That, आहुः (they) say, परमाम् the highest, गतिम् goal (path), यम् which, प्राप्य having reached, न not, निवर्तन्ते return, तत् that, धाम abode (place or state), परमम् highest, मम My.

Commentary:
Para Brahman is called the Unmanifested because It cannot be perceived by the senses. It is called the Imperishable also. It is allpervading, allpermeating and interpenetrating. Para Brahman is the highest Goal. There is nothing higher than It. This is the true nondual state free from all sorts of limiting adjuncts. The attainment of Brahmaloka (the region of the Creator) etc., is inferior to this. Only by realising the Self is one liberated from Samsara. (Cf.XII.3,XV.6)