Sahih Muslim , Book 4, Hadith 794 (USC-MSA) ⓘ
Shu'ba has narrated this on the authority of Mansur with the same chain of transmitters, but he made no mention of this: " Then he may choose any supplication which pleases him."
حَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، وَابْنُ، بَشَّارٍ قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ مَنْصُورٍ، بِهَذَا الإِسْنَادِ مِثْلَهُ وَلَمْ يَذْكُرْ " ثُمَّ يَتَخَيَّرُ مِنَ الْمَسْأَلَةِ مَا شَاءَ " .
also referenced under: Book 4, Hadith 60 (In-Book) & Hadith 402 (Reference)