نهج البلاغه Aimr al-Mu'minin, peace be upon him, said : The eye is the strap of the rear. Al-Sayyid al-Radi says : This is a wonderful meraphor, it is as though Amir al-Mu'minin, has likened the rear part of the body with a bag and the eye with a strap. When the strap is let loose the bag cannot retain anything. According to the well-known and reputed view it is the saying of the Peophet but some people have stated it to be of Amir al-Mu'minin. al-Mubarrad has mentioned it in his book al-Mubarrad under the chapter Words of single letters. We too have discussed this metaphor in our book named Majazat al-athar al-nabawiyyah.