It is narrated from Sayyiduna Abdullah bin Mas’ud (may Allah be pleased with him), he says: We were sitting with the Messenger of Allah (peace and blessings be upon him) in the Cave of Hira, when Surah {وَالْمُرْسَلَاتِ عُرْفًا} was revealed to him. We were learning that Surah from him when suddenly a snake appeared from the side of the cave. The Prophet (peace and blessings be upon him) said: Kill it. We rushed towards it but it escaped from us. The Prophet (peace and blessings be upon him) said: It remained safe from your harm and you from its harm.