Muslim religious authorities speak about three levels of fasting – Firstly, the ‘outward fast’, where one abstains from food, drink and sexual union. Secondly, the ‘fasting of the limbs’, whereby the eyes, ears, tongue, hands and feet refrain from sins and acts of disobedience. Thirdly, and it is the highest degree of fasting, the ‘fasting of the soul’, where the above practices are perfected by an abstinence from any thought that may hinder constant awareness of God’s presence:
Fasting is enjoined on you, as it was enjoined on those before you, that you may perhaps become God-conscious.
The first two levels of fasting are types of abstinence that Islam commands as a duty. It is the third level, however, which is the sought after goal.
One of the finest treatments on the inward aspects of fasting was penned for us by Imam al-Ghazali (d.505H/1111CE) in his remarkable fusion of Muslim law, ethics and spirituality, ’Revival of the Religious Sciences’. What follows is a translation of his opening comments on the subject:
Realise that there are three degrees of fasting: the fasting of the generality, the fasting of the elite and the fasting of the elect.
The fasting of the generality involves the stomach and the genitals refraining from indulging their passions, as has previously been explained.
The fasting of the elite involves keeping one’s ears, eyes, tongue, hands, feet, all the organs, free from sin.
As for the fasting of the elect, it is the fasting of the heart from all unworthy concerns or worldly thoughts; a total abstinence from all else besides God, Mighty and Majestic is He. Such a fast is broken by thinking about other than God or the Afterlife; or by thinking about worldly matters – except those worldly thoughts conducive to religious ends, for these constitute provisions for the Afterlife and are not of this lower world. Masters of the heart have even said, “A sin is recorded against he who spends his day concerned with what arrangements he has to break his fast.” This is because it shows a lack of trust in God’s grace and a lack of certainty in His promised livelihood. To this [third] degree belong the Prophets, saints and those drawn near to God. We need not dwell on the description of this type of fasting, since its true nature is best revealed in action. It is to be wholly dedicated to God and to turn away from all else other than Him. It is to embody the words of God, when He said, ‘Say: “God” then leave them to play in their vain discourse and trifling.’
 al-Qur’an 2:183