Appears 3 times in the Quran. (Root: دبر)
  1. And had you seen when the angels will cause to die those who disbelieve, smiting their faces and their backs, and (saying): Taste the punishment of burning.

  2. Therefore go forth with your followers in a part of the night and yourself follow their rear, and let not any one of you turn round, and go forth whither you are commanded.

  3. But how will it be when the angels cause them to die smiting their backs.