St. John Cassian: It is first of all necessary to purify carefully the hidden recesses of our heart...

It is first of all necessary to purify carefully the hidden recesses of our heart. 

For that which we desire to gain by bodily purity we must possess in the depths of our conscience, where the Lord resides as judge and superintendent of the games He carefully observes how we run and fight. 

Thus those things which we are loathe to admit in the open will not even take shape in our interior and we will not even be soiled by any secret connivance. 

For although it might escape the notice of men, it cannot lie hidden from the knowledge of Almighty God and the holy angels, from whom no secret is hidden.

St. John Cassian