Matthew 6:16-18 (NASB)
Fasting; The True Treasure; Wealth (Mammon)
16 “Whenever you fast, do not put on a gloomy face as the hypocrites do, for they neglect their appearance so that they will be noticed by men when they are fasting. Truly I say to you, they have their reward in full. 17 But you, when you fast, anoint your head and wash your face 18 so that your fasting will not be noticed by men, but by your Father who is in secret; and your Father who sees what is done in secret will reward you.
Isaiah 58:3-7 (NASB)
3 ‘Why have we fasted and You do not see?
Why have we humbled ourselves and You do not notice?’
Behold, on the day of your fast you find your desire,
And drive hard all your workers.
4 “Behold, you fast for contention and strife and to strike with a wicked fist.
You do not fast like you do today to make your voice heard on high.
5 “Is it a fast like this which I choose, a day for a man to humble himself?
Is it for bowing one’s head like a reed
And for spreading out sackcloth and ashes as a bed?
Will you call this a fast, even an acceptable day to the Lord?
6 “Is this not the fast which I choose,
To loosen the bonds of wickedness,
To undo the bands of the yoke,
And to let the oppressed go free
And break every yoke?
7 “Is it not to divide your bread with the hungry
And bring the homeless poor into the house;
When you see the naked, to cover him;
And not to hide yourself from your own flesh?