Pope Shenouda III
Fasting without mercy and charity is unacceptable:
The Lord explained this point to the Prophet Isaiah, saying: “`Why have we fasted,' they say, `and You have not seen? Why have we afflicted our souls, and You take no notice?'
... Indeed you fast for strife and debate ... Is it a fast that I have chosen, A day for a man to afflict his soul? ...Would you call this a fast, And an acceptable day to the Lord? “Is this not the fast that I have chosen: To loose the bonds of wickedness, To undo the heavy burdens, To let the oppressed go free, And that you break every yoke? Is it not to share your food with the hungry and to provide the poor wanderer with shelter--” (Is 58:3-7).
A fast that does not go hand in hand with merciful deeds and a pure heart is unacceptable even if performed with humility and courtesy.