[2:183] O you who believe, prescribed for you is the Fast, just as it was prescribed for those that were before you so that you might guard yourselves.
Fasting is of two types: the external fast which is abstention from things that break the fast accompanied by the intention [to fast], and the inner fast which is preserving the heart from harm, then the preservation of the spirit from familiar comforts (musākanāt), and then the preservation of the inner self from considerations (malāḥaẓāt).
It is said the requirement of the fasting of worshippers, if it is to be complete, is preserving the tongue from slander (ghība), and preserving the glance from viewing with suspicion (rība), as it is said in the tradition, 'Whoever fasts, let him fast with his ears, his eyes...'. As for the fast of those who know, it is protecting the innermost self from witnessing anything other than Him.
For those who abstain from the things that break the fast, the end of their fast is when night falls. For those who fast from everything other [than Him], the end of their fast is that they witnesses the Real. He (ṣ) said, 'Fast to see Him and break your fast to see Him'. [In this ḥadīth the letter] hāÌ in his words (ṣ) li-ruÌyatihi refers, according to the people of realization (ahl al-taḥqīq), to the Real (s). The religious scholars (ʿulamāÌ) say its meaning is 'Fast when you see the new moon of Rama?ān and break your fast when you see the new moon of Shawwāl'. As for the elect, their fast is for God because of their witnessing God, and their breaking of the fast is through God, and their approach is to God and the One Who prevails over them is God and the One through Whom they are effaced is God.