حَدَّثَنَا الْقَعْنَبِيُّ، عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏"‏ لاَ يَقُولَنَّ أَحَدُكُمُ اللَّهُمَّ اغْفِرْ لِي إِنْ شِئْتَ اللَّهُمَّ ارْحَمْنِي إِنْ شِئْتَ لِيَعْزِمِ الْمَسْأَلَةَ فَإِنَّهُ لاَ مُكْرِهَ لَهُ ‏"‏ ‏.‏

Abu Hurairah reported the Messenger of Allah (PBUH) as saying: "One of you should not say (in his supplication): O Allah, forgive me if You please, show mercy to me if You please.' Rather, be firm in your asking, for no one can force Him." Translation Not Available

Book Ref: Sunan Abi Dawud Book 8 Hadith 1483
Web Ref:  Sunan Abi Dawud Book 8 Hadith 1478