It is narrated from Sayyiduna Ibn Mas'ud (may Allah be pleased with him) that once we were with the Prophet (peace and blessings be upon him) in a cave, and there Surah Mursalat was revealed to the Prophet (peace and blessings be upon him). We began to memorize it after hearing it from the Prophet (peace and blessings be upon him). Suddenly, a snake came out of its hole. The Prophet (peace and blessings be upon him) said: "Kill it." We quickly moved forward, but it got ahead of us and slipped into its hole. The Prophet (peace and blessings be upon him) said: "Allah has saved it from your harm just as He has saved you from its harm."