The answer
Fasting is the bowing down of the whole human being before the Holy Spirit that He may sanctify him. God does not desire the destruction of the body, but its sanctification. Thus, in addition to bodily fasting, the believer practices holy spiritual fasting, through which the soul is liberated from all impurities and becomes able to ascend freely towards heaven. St. John Cassian writes, “We ought therefore, whenever the outward man fasts, to restrain the inner man as well from food which is bad for him: that inner man, namely, which the blessed Apostle above all urges us to present pure before God, that it may be found worthy to receive Christ within.”428
Fr. Tadros Yacoub Malaty
Notes
428 St. John Cassian, Institutes 5.21 (NPNFII/11:241).