The grace of the Holy Spirit which is given mystically to every Christian when he is baptized acts and is manifested in proportion to our obedience to the commandments of the Lord. That is, if a Christian obeys the commandments of the Lord more, grace acts with him more, while if he obeys them less, grace acts within him less. Just as a spark, when covered in the ashes of fire becomes increasingly manifest as one removes the ashes, and the more fire wood you put the more the fire burns, so the grace that has been given to every Christian through Holy Baptism is hidden in the heart and covered up by the passions and sins, and the more a man acts in accordance with the commandments of Christ, the more he is cleansed of the passions and the more the fire of Divine grace lights in his heart, illumines and deifies him.

St. Nicodemus of the Holy Mountain