Authentic
hadith of Sahih Muslim
Sahih Muslim 402c
حَدَّثَنَا عَبْدُ بْنُ حُمَيْدٍ، حَدَّثَنَا حُسَيْنٌ الْجُعْفِيُّ، عَنْ زَائِدَةَ، عَنْ مَنْصُورٍ، بِهَذَا الإِسْنَادِ مِثْلَ حَدِيثِهِمَا وَذَكَرَ فِي الْحَدِيثِ " ثُمَّ لْيَتَخَيَّرْ بَعْدُ مِنَ الْمَسْأَلَةِ مَا شَاءَ أَوْ مَا أَحَبَّ " .
This hadith has been narrated on the authority of Mansur with the same chain of transmitters and he made a mention of this:
" Then he may choose any supplication which pleases him or which he likes."
Reported by Muslim (No. 402c).