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