Hadithcore
Sahih Muslim, 1226 b
sahih

This hadith been narrated on the authority of Jurairi with the same chain of transmitters, and Ibn Hatim said in his narration:

" A person said according to his personal opinion, and it was Umar."

وَحَدَّثَنَاهُ إِسْحَاقُ بْنُ إِبْرَاهِيمَ، وَمُحَمَّدُ بْنُ حَاتِمٍ، كِلاَهُمَا عَنْ وَكِيعٍ، حَدَّثَنَا سُفْيَانُ، عَنِ الْجُرَيْرِيِّ، فِي هَذَا الإِسْنَادِ وَقَالَ ابْنُ حَاتِمٍ فِي رِوَايَتِهِ ارْتَأَى رَجُلٌ بِرَأْيِهِ مَا شَاءَ ‏.‏ يَعْنِي عُمَرَ ‏.‏

References2 variants
In-Book Reference
Book 15, Hadith 182
USC-MSA web (English) reference
Book 7, Hadith 2825 (deprecated numbering scheme)