Authentic
Sunan Ibn Majah 1385
“Pray to Allah to heal me.” He said: “If you wish to store your reward for the Hereafter, that is better, or if you wish, I will supplicate for you.” He said: “Supplicate.” So he told him to perform ablution and do it well, and to pray two Rak’ah, and to say this supplication: “Allahumma inni…
" إِنْ شِئْتَ أَخَّرْتُ لَكَ وَهُوَ خَيْرٌ وَإِنْ شِئْتَ دَعَوْتُ " . فَقَالَ ادْعُهْ . فَأَمَرَهُ أَنْ يَتَوَضَّأَ فَيُحْسِنَ وُضُوءَهُ وَيُصَلِّيَ رَكْعَتَيْنِ وَيَدْعُوَ بِهَذَا الدُّعَاءِ " اللَّهُمَّ…