Verse 13of 50

Which was revealed in MakkahThe Revelation of this Surat and its Recitation in the Maghrib PrayerAl-Bukhari recorded from `Abdullah - that is Ibn Mas`ud -- that he said, "While we were with the Messenger of Allah ﷺ in a cave at Mina,وَالْمُرْسَلَـتِ(By the Mursalat.) was revealed to him. He was reciting it and I was learning it from his mouth. Verily, his mouth was moist with it when a snake leaped out at us. The Prophet said,«اقْتُلُوهَا»(Kill it!) So we quickly went after it, but it got away.

Source: Tafsir Ibn Kathir — abridged excerpt