Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.112B.
Section : Supplicating with confidence in its acceptance..
Abu Hurairah also reported that the Prophet, peace be upon him, said, “None of you should say, ‘O Allah, forgive me if You wish, (or) O Allah, have mercy on me if you wish.’ Rather you should be firm in your request, for (Allah does whatever He wishes) and no one can force Him to do otherwise.”