Link:- In the preceding verse, the Lard declared the worshippers of God with form and attributes, to be the best Yogis. So a question arises, whether worshippers of attributeless Absolute (Brahma), are not the best Yogis.
The Lord, answers the question, in the next two verses:
ye tvaksaramanirdesyamavyaktam paryupasate
sarvatragamacintyath ca katasthamacalam dhruvam
sanniyamyendriyagramam sarvatra samabuddhayah
te prapnuvanti mameva sarvabhutahite ratah
But those, who worship the Imperishable (Aksara), the Undefinable, the Unmanifest, the Omnipresent, the incomprehensible, the Unchanging and the Immobile, the constant, by restraining all the senses, being even-minded everywhere, engrossed in the welfare of all beings, also come to Me. 3-4
The term Tu' (but), shows that worshippers of the formless Brahma, are different from those, who worship the Lord with form.
Sanniyamyendriyagramam:- Having given the term 'Sanniyamya', with two prefixes 'Sam' and 'Ni' the Lord, lays emphasis on full control over all senses. If they are not fully controlled, there is difficulty in the worship of attributeless Absolute. The senses of devotees who worship the Lord with attributes, are fixed on Him and so there is not much need of controlling the senses, as for devotees who worship attributeless Brahma. Such devotees, having no base for thought, without controlling the senses, can think of the objects of senses, and thus can perish (Gita 2/62-63). Therefore, for devotees who worship the attributeless God, it is necessary to control, not only the senses fully, but also the mind, because so long as, there is attachment of the mind with the objects of senses, the Absolute (Brahma), cannot be attained (Glib 15/11).
In the Gita, control over senses has been considered very essential, in the Disciplines of Knowledge and Action. There is no such stress in the Discipline of Devotion.
Acintyam:- The term stands for the Absolute, Who is beyond the reach of senses and mind, because they being evolutes of prakrti cannot even know and think of prakrti; then how can they know and think of God, Who transcends prakrti (Nature)? God can be known, only by the self.
Sarvatragam:- God is all-pervading and limitless. So, he cannot be attained, by limited mind, intellect and senses.