From the Masnavi of Jalaluddin Rumi

Hidden sweetness lies in an empty stomach, Man is like a lute, not more not less

When the lute’s stomach is full, it cannot lament, whether high or low.

When your head and stomach burn with fasting, The fire draws lamentation from your breast.

The fire will burn thousands of veils each time you ascend a thousand degrees.

On the way and in your ambition, Keep your stomach empty! Lament like a flute

Tell God your need! Keep your stomach empty, speak of the mysteries like the reed!

When the stomach is full, it calls Satan to you, instead of the intellect an idol, instead of the Kaaba the devil.

When you fast, qualities of character gather round you like servants, slaves and followers.

Continue your fasting, for its Solomon’s seal, don’t give the seal to the devil, don’t disrupt your kingdom.