Muwatta Malik 497

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 ‏"‏ ‏.‏

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

Reference

Muwatta Malik 497

In-book

Book 15, Hadith 28