سنن النسائي

It was narrated that Ibn Abbas said: "When Jibril was with the Messenger of Allah (ﷺ), he heard a sound from above like a door opening. Jibril, peace be upon him, looked up toward the sky and said: 'This is a gate in Heaven that has been opened, but it was never opened before." He said: "An Angel came down from it and came to the Prophet (ﷺ) and said: 'Receive the glad tidings of two lights that have been given to you and were never given to any prophet before you: The Opening of the Book (Al-Fatihah) and the last verses of Surat Al-Baqarah. You will never recite a single letter of them but you will be granted it.'"