In this concluding verse Krishna says that He has taught in this chapter ‘THE MOST SECRET SCIENCE.’ The spiritual science (Brahma-vidya) is termed as ‘secret,’ not in the sense that it should not be given out to anybody, but that it is a knowledge which cannot, of its own accord come to anyone, unless one is initiated into it by a ‘Knower of Reality.

‚Äô O SINLESS ONE — ‘Sin’means an act, a feeling or a thought, which having been perpetrated, entertained, or thought of, comes back after a time to agitate our bosom with its insulting taunts and helpless regrets. In short, SIN is the resultant of the past that comes to demean our self-estimate and creates in us a lot of mental storm and consequent dissipation. One who has thus an inner personality which carries disturbing memories of undignified acts and cruel schemes, has indeed, a bosom that is ever agitated and restless. Such a mind-intellect-equipment cannot consistently apply itself to any serious and deep investigation into the subtle realm of the Pure Awareness that lies beyond the frontiers of the intellect. Therefore, the term ‘sinless’ in the context here only means “O STEADY-MINDED, ALERT AND VIGILANT STUDENT.”
He who has realised this PURUSHOTTAMA-STATE of Consciousness becomes ‘wise,’ for he cannot thereafter make any error of judgement in life and thereby create confusions and sorrows for himself and for others around him.
The second of the benefits accrued by entering the Purushottama State is the enjoyment of a complete sense of fulfilment (Krita-krityataa) — a total and overwhelming joy that comes to a man when he realises that he has fully accomplished what is expected of him. This is promised here in this verse as the reward for the realisation of the Purushottama-stage.

This guhyatamam, most secret, i.e. most mystical;- what is that?-sastram, scripture-. Although the Gita as a whole is spoken of as the scripture, still this chapter itself is here referred to as such, and this for eulogy as is evident from the context. For, not only has the entire meaning of the scripture Gita been stated here in brief, but the whole purport of the Vedas also has been comprehended here. And it has been said, ‘He who realizes it is a knower of the Vedas’ (1), ‘I alone am the object to be known through all the Vedas’ (15). (Thus, this most secret scripture) iti uktam, has thus been uttered; maya, by Me; anagha, O sinless one. O scion of the Bharata dynasty, buddhva, under-standing; etat, this, the scripture which has the purport as has been revealed; syat, one becomes; buddhiman, wise; and krta-krtyah, has his duties fulfilled; but not otherwise. The meaning is that what-ever a Brahmana has to do as a consequence of his special birth (as a Brahmana), all that becomes accomplished when the reality of the Lord is known. The idea is that nobody’s duties become fulfilled in any other way. And it has been said, ‘O son of Prtha, all actions in their totality culminate in Knowledge’ (4.33). There is also a saying from Manu: ‘This, verily, is the fulfilment of a Brahmana in particular. For, by getting this, a twice-born has his duties fulfilled; not otherwise’ (Ma. Sm. 12.93). Since you have heard from Me this truth about the supreme Reality, therefore, O scion of the Bharata dynasty, you have achieved your Goal!