Abu sa'id Ar-Rafi bin Al Mu'allah (ra) reported: The Messenger of Allah (salla-Llaahu 'alayhi wa-sallam) said, "Shall I teach you the greatest Surah in the Qur'an before you leave the mosque?" Then He (salla-Llaahu 'alayhi wa-sallam), took me by the hand, and when we were about ot step out, I...