Muwatta Malik, Book 15, Hadith 28 (USC-MSA) ⓘ

Yahya related to me from Malik from Abu'z Zinad from al-Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, said, ''When you are making dua do not say; 'O Allah, forgive me if You wish. O Allah, forgive me if you wish.' You should be firm in your asking, for there is no compelling Him."

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ لاَ يَقُلْ أَحَدُكُمْ إِذَا دَعَا اللَّهُمَّ اغْفِرْ لِي إِنْ شِئْتَ اللَّهُمَّ ارْحَمْنِي إِنْ شِئْتَ لِيَعْزِمِ الْمَسْأَلَةَ فَإِنَّهُ لاَ مُكْرِهَ لَهُ ‏" ‏ ‏.‏