in his will to his son, al-Hasan (AS), ?O My son, shall I teach you four things which will make you needless of medicine?' He replied, 'Yes, O Commander of the Faithful.' So he said, 'Do not sit to eat unless you are hungry. Stand up from the table while you still desire food. Chew properly. Go to the lavatory before you go to bed. If you put these into practice, you will not need medicine.'