The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَزُهَيْرُ بْنُ حَرْبٍ، جَمِيعًا عَنِ ابْنِ عُلَيَّةَ، قَالَ أَبُو بَكْرٍ حَدَّثَنَا إِسْمَاعِيلُ ابْنُ عُلَيَّةَ، عَنْ عَبْدِ الْعَزِيزِ بْنِ صُهَيْبٍ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا دَعَا أَحَدُكُمْ فَلْيَعْزِمْ فِي الدُّعَاءِ وَلاَ يَقُلِ اللَّهُمَّ إِنْ شِئْتَ فَأَعْطِنِي فَإِنَّ اللَّهَ لاَ مُسْتَكْرِهَ لَهُ " .Anas reported Allah's Messenger (ﷺ) as saying:When one of you makes supplication, he should supplicate with a will and should not say: O Allah, confer upon me if Thou likest, for there is none to coerce Allah
From Sahih Muslim, whose reports the scholars accept as authentic.