Who suggested to dig a ditch around city of Medina?

Who suggested to dig a ditch around city of Medina?

مدینہ شہر کے ارد گرد کھائی کھودنے کا مشورہ کس نے دیا؟
Explanation
  1. On the recommendation of Hazrat SALMAN FARSI, a trench was dug around the base of MEDINA to protect all the approaches.
  2. The pagans of MECCA had failed to annihilate the Muslim base of MEDINA in the battle of UHUD, SHAW AL 3 HURA.