What invocation did the Prophet Muhammad (saw) often use to invoke Allah?
 Narrated Abu Musa:                     The Prophet used to invoke Allah with the following invocation: 'Rabbi-ghfir-li Khati 'ati wa jahli wa israfi fi `Amri kullihi, wa ma anta a'lamu bihi minni. Allahumma ighfirli khatayaya wa 'amdi, wa jahli wa jiddi, wa kullu dhalika'indi. Allahumma ighrifli ma qaddamtu wa ma akhartu wa ma asrartu wa ma a'lantu. Anta-l-muqaddimu wa anta-l-mu'akh-khiru, wa anta 'ala kulli shai'in qadir.'