Three Classes of Fasting

There are three classes of the Fasting.
1. Fast of the general Muslims. It is to restrain oneself from eating and drinking and from sexual passion. This is the lowest kind of Fasting.
2. Fasting of the few select Muslims. In this kind of Fasting, besides the above things one refrains himself from sins of hand , feet, sight and other limbs of body.
3. Fasting of the highest class. These people keep fast of mind. In other words, they don't think of anything else except God and the next world. They think only of the world with the intention of the next world as it is the seed ground of the future.

[Imam Gazali: Ihya-uloomidheen.]