Sahih (Sahih al-Bukhari)
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ عَبْدِ الْعَزِيزِ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا دَعَوْتُمُ اللَّهَ فَاعْزِمُوا فِي الدُّعَاءِ، وَلاَ يَقُولَنَّ أَحَدُكُمْ إِنْ شِئْتَ فَأَعْطِنِي، فَإِنَّ اللَّهَ لاَ مُسْتَكْرِهَ لَهُ ".
Narrated Anas:Allah's Messenger (ﷺ) said, "Whenever anyone of you invoke Allah for something, he should be firm in his asking, and he should not say: 'If You wish, give me...' for none can compel Allah to do something against His Will