Abd al-Rahman bin Abi Layla (may Allah have mercy on him) said: The Companions (may Allah be pleased with them) of the Prophet (peace and blessings be upon him) told us that they were travelling with the Prophet (peace and blessings be upon him) (they were on a journey). One of them fell asleep, and some of the Companions (may Allah be pleased with them) took a rope with which they frightened him, and he became alarmed. The Prophet (peace and blessings be upon him) said: "La yahillu li-muslimin an yurawwi'a musliman" (It is not lawful for a Muslim to frighten his Muslim brother).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الشهادات / 21177