He Smiled when ‘A'ishah was Keen to Know Allah's Most Supreme Name

It has been narrated that ‘A'ishah, may Allah be pleased with her, said,

“I heard the Messenger of Allah (Peace be upon him) saying,

‘O Allah! I ask You with Your Name which is pure, good, and blessed, which is the dearest (Name) to You, and by virtue of which You respond to invocation if You are invoked with it, give (those who ask You for things) if You are asked with it, have mercy (upon those who ask You for mercy) if You are asked for mercy with it, and drive away (worries, grief, etc.) if You are asked for that with it.’”

She also said,

"And once he said, ‘O ‘A'ishah, do you know that Allah has guided me to the Name with which He responds to invocation if He is invoked with it?' I said, 'O Messenger of Allah — I ransom you with my father and my mother — let me know it.’ He said, 'You should not (know) it, O ‘A'ishah’ So, I stepped aside and sat for an hour (i.e., for some time) then stood up and turned his head around, then I said, ‘O Messenger of Allah, let me know it.’ He said, 'You should not (know) it (nor should I) let you know it. (Also,) you should not ask for anything related to worldly life with it.’ Therefore, I performed ablution then performed two rak’ahs (units of prayer) then said, ‘O Allah! I invoke You as the All-Merciful, I invoke You as Al-Barr (the Most Subtle, Kind, Courteous, and Generous) and the Ever Merciful, and I invoke You with all Your Most Beautiful Names, including what I know of them and what I do not know, to forgive me and have mercy upon me!' The Messenger of Allah (Peace be upon him) smiled then said, 'It is one of the Names with which you have (just) invoked (Allah).’" [Transmitted by Ibn Majah, No. 3943]