And so he speaks to them again concerning these things, "Why do you fast for me, says the Lord, so that your voice is heard crying out today?  This is not the fast I have chosen , says the Lord—not a person humbling his soul.
Not even if you bend your neck into a circle and put on sackcloth and make for yourself a bed of ashes—not even so should you call this a proper fast".

Some people think by showing outward signs of piety and devotion such as fasting, praying in public, wearing religious jewelry, etc., that they are being pious and devoted to God.  But this bit of Gnostic scripture disagrees.   All the outward signs of devotion are meaningless if you haven't truly devoted yourself to God in humility and honesty.  Matthew says much the same in Matthew 6:5-6.