Mishkat al-Masabih 2259
Abu Sa'id al-Khudri reported the Prophet as saying, “Any Muslim who makes a supplication containing nothing which is sinful or which involves breaking ties of relationship will be given for it by God one of three things:
He will give him as peedy answer, or store it up for him in the next world, or turn away from him an equivalent amount of evil.” Those who heard it said they would then make many supplications and he replied that God was more ready to answer than they were to ask.

Ahmad transmitted it.
وَعَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: 
" مَا مِنْ مُسْلِمٍ يَدْعُو بِدَعْوَةٍ لَيْسَ فِيهَا إِثْمٌ وَلَا قَطِيعَةُ رَحِمٍ إِلَّا أَعْطَاهُ اللَّهُ بِهَا إِحْدَى ثَلَاثٍ: إِمَّا أَنْ يُعَجِّلَ لَهُ دَعْوَتَهُ وَإِمَّا أَنْ يَدَّخِرَهَا لَهُ فِي الْآخِرَةِ وَإِمَّا أَنْ يَصْرِفَ عنهُ من السُّوءِ مثلَها " قَالُوا: إِذنْ نُكثرُ قَالَ: «الله أَكثر» . رَوَاهُ أَحْمد