Know then that moderate exercise is a most potent means of preserving health. It warms the organs and dissolves waste products and renders the body light and active. The time for this is after the descent of the food from the stomach. It accomplishes this in five or six hours, more or less according to the constitution of the individual and of the food. By moderate exercise is meant exercise which makes the skin red and glow. When sweating begins, then it is proper to cease. That which increases the sweat is called violent exercise. Every organ is strengthened and enlivened by much exercise. The same is true of the internal faculties.

Whoever wishes to increase his memory will increase it by memorising. The same things applies to the under-
standing and to thought. So, for every organ there is a specific exercise. Thus, for the chest there is talk, beginning with whispering and passing to shouting. For the eyes there are small letters. And for hearing there are soft, pleasing sounds. Horse-riding is moderate exercise for the whole body. The Prophet has proposed for us an exercise which corrects our bodies Folio I9 ard our hearts, when he said: Raid and you will get rich: travel and you will get health. And again he said: Fasting brings health. His saying has already been quoted: Dissolve your food with pious practices and prayer. A Regime for Sleep The best time to go to sleep is after the digestion of food. It is wise to go to sleep first on the right side, as the Prophet used to do. This was
confirmed by (Ayesha when she said: He first used to go to sleep on the right side looking towards Mecca. Sleep by day is bad. It damages the complexion, gives rise to diseases and renders a man lazy. It is to be avoided except in the mid-day heat according to the saying of the Prophet: Go ye to sleep, for the devils never sleep. And again he said: Make easier your rising for prayer during the night by taking a short sleep during the day. He also said: Sleep in the morning is a hindrance to the daily bread. Jabir relates that the Prophet forbade a man to sleep part in the sun and part in the shade. Among the traditions is that he also forbade a man to sit part in the sun and part in the sahe. These are the statements of al-Haifiz