12.3 Ye, those; tu, however; who, pari-upasate, meditate in every way; aksaram, on the Immutable; anirdesyam, the Indefinable-being unmanifest, It is beyond the range of words and hence cannot be defined; avyaktam, the Unmanifest-It is not comprehensible thrugh any means of knowledge-.
Upasana, meditation, means approaching an object of meditation as presented by the scriptures, and making it an object of one's own thought and dwelling on it uniterruptedly for long by continuing the same current of thought with regard to it-like a line of pouring oil. This is what is called upasana.
The Lord states the characteristics of the Immutable [Here Ast. adds 'upasyasya, which is the object of meditation'.-Tr.] : Sarvatragam, all-pervading, pervasive like space; and acintyam, incomprehensible-becuase of Its being unmanifest. For, whatever comes within the range of the organs can be thought of by the mind also. Being opposed to that, the Immutable is inconceivable. It is kutastham, changeless. Kuta means something apparently good, but evil inside. The word kuta (deceptive) is well known in the world in such phrases as, 'kuta-rupam, deceptive in appearance,' 'kuta-saksyam, false evidence', etc. Thus, kuta is that which, as ignorance etc., is the seed of many births, full of evil within, referred to by such words as maya, the undifferentiated, etc., and well known from such texts as, 'One should know Maya to be Nature, but the Lord of Maya to be the supreme God' (Sv. 4.10), 'The divine Maya of Mine is difficult to cross over' (7.14), etc. That which exists on that kuta as its controller (or witness) is the kuta-stha. Or, kutastha may mean that which exists like a heap [That is, motionless.].
Hence it is acalam, immovable. Since It is immovable, therefore It is dhruvam, constant, i.e. eternal.