Verse 1

1. Then Ashvalayana addressed the Lord and said: "Teach,  O Lord,  the knowledge of the Absolute,  the highest,  always cultivated by the good,  secret and by which a wise man drives away instantly all the sins and reaches the Absolute higher than the high".

"Then Ashvalayana addressed the Lord and said Teach,  O Lord,  the knowledge of the Absolute,  the highest"

When Ashvalayana is moved to sound his desire for knowledge and union with the Absolute it is that seed of Divinity that is maturing.  Kaivalya itself is the fruition of purpose and realisation of life's journey.

"always cultivated by the good".

The knowledge of the Absolute which Ashvalayana desires is that same knowledge that all the good and wise cultivate or nurture from within their being.  The good are the ones that can discriminate between transient material truth and eternal truth.
The intuition that this higher truth exists is the beginning of wisdom.

"secret"

That described as secret means that understanding that is subtle and can only come from within ones own self,  arising from ones own intuition,  albeit helped and guided by the Guru in revealing the subtle meaning within the words of the scriptures. 

"by which a wise man drives away instantly all the sins"

When the word sin is used,  especially within the Upanishads its meaning is understood by us to be any action or practice that might cause forgetting of the Absolute Self or delay ones inevitable attainment of that truth.  There would be no big sin or little sin.  A sin is just an action or way that is,  for the moment,  in ignorance of the Absolute. 
Needless to say "sins" fall away with the wisdom that comes with truth.  Further,  abiding in the truth the wise person naturally "drives away instantly" all further untruth with its sins.

"and reaches the Absolute higher than the high"

Truth is seen or discriminated through the cleansed Buddhi or intellect.  This highest Truth of Non-Duality contains the understanding that the duality of high and low does not exist in reality,  this is indeed the light that leads to the Realisation of "The Absolute higher than the high".

This is a plea for freedom made by one who is world weary because he has realised that this experience of life does not reflect the highest truth.
It is for our benefit here that Ashvalayana seeks and receives the Truth that sets you free and as an example he is willing to suffer any trial to attain that truth.