Sahih Muslim 2678
Sahih Muslim · Book 48: The Book Pertaining to the Remembrance of Allah, Supplication, Repentance and Seeking Forgiveness · Being Firm In Supplication And Not Saying: "If You Will"
Anas reported Allah's Messenger (ﷺ) as saying:
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 " .
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.