Abu Dawud Book 36, Hadith Number 4986.

Narated By AbdurRahman ibn AbuLayla : The Companions of the Prophet (PBUH) told us that they were travelling with the Prophet (PBUH). A man of them slept, and one of them went to the rope which he had with him. He took it, by which he was frightened. The Prophet (PBUH) said: It is not lawful for a Muslim that he frightens a Muslim.