According to St. Paul, it is characteristic of the Spirit of life to act and to speak in the heart, while a literal, outwardly correct observance of things characterizes the fallen unregenerate person (cf. Rom. 8:2; Cor. 3:6). The Spirit of life frees the nous from sin & death, whereas a literal, outwardly correct observance imperceptibly turns us into pharisees, since we then act only in an external bodily sense & practice the commandments merely in order to be seen doing so (Matt. 23:5).
—St. Gregory of Sinai