It was narrated that 'Aishah said: "I heard the Messenger of Allah (saas) say: 'Allahumma! Inni asa'luka bismikat-tahirit-tayyibil-mubarak al-ahabbi ilaika, alladhi idha du'ita bihi ajabta, wa idha su'ilta bihi a'taita, wa idhasturhimta bihi rahimta, wa idhastufrijta bihi farrajta (O Allah! I ask You by Your pure, good and blessed Name which is most beloved by You, which if You are called thereby You answer, and if You as asked thereby You give, if You are asked for mercy thereby You bestow mercy, and if You are asked for relief (from distress) thereby You grant relief.'"She said: "He said one day: 'O 'Aishah, do you know that Allah has told me the Name which, if He is called thereby, He responds?' I said: 'O Messenger of Allah, may my father and mother be ransomed for you! Teach it to me.' He said: 'You should not learn it, O 'Aishah.' So I moved aside and sat for a while, then I got up and kissed his head, then I said: 'O Messenger of Allah, teach it to me.' He said: 'You should not learn it, O 'Aishah, and I should not teach it to you, for you should not ask for any worldly things thereby.'" She said: "So I got up and performed ablution, then I prayed two Rak'ah, then I said: 'O Allah, I call upon Allah, and I call upon You, Ar-Rahman (the Most Gracious), and I call upon You, Al-Barr Ar-Rahim (The Most Kind, the Most Merciful), and I call upon You by all Your beautiful Names, those that I know and those that I do not know, (asking) that You forgive me and have mercy on me.' The Messenger of Allah (saas) smiled, then he said: 'It is among the names by which you called upon (Allah).'"