The reason and purpose for cleansing the mind is that the human mind is an illusion and false.
If one gets rid of the illusionary, false mind, is born into the world, and lives, one's life in this world will be that of boundless comfort and freedom.
One is born into this eternally living, immortal world and lives without death - how fortunate is this?
Until now, there has not been a way to cleanse the mind, but now there is a method to eliminate the mind. When there is no mind, you will have wisdom, and you will always be happy.
The human mind consists of the karma, habits and body.
When one discards the karma, habits, and body within, only Truth remains. And when one is reborn in the Land of Truth, one achieves human completion and eternally never dies.
This is the era of human completion. To cleanse the mind means to eliminate the false mind- this is what it means to cleanse.
When you do meditation to eliminate the false mind, you can achieve completion.