أﻣﻞ إﺑﻠﻴﺲ ﺑﺎﻟﺠﻨﺔ

From the Art of Speech by Hussein Maxos:

  أﻣﻞ إﺑﻠﻴﺲ ﺑﺎﻟﺠﻨﺔ
(amal eeblees biljinna)
Literal meaning: hope of the devil in heaven
Meaning: describes something impossible. An equivalent might be "A snowball's chance in hell"