Musnad Ahmad 455, 456
It was narrated from Hisham bin `Urwah from his father from Marwan, and we have no reason to suspect hirn, who said,  `Uthman (رضي الله عنه) suffered a nosebleed in the year of the nosebleed, (which was so bad that, he stayed behind from Hajj and gave his final instructions (because he thought he was going to die). A man of Quraish entered upon him and said:
Appoint a successor. He said: Are they suggesting that? He said: Yes. He said: Who are they suggesting? The man kept quiet. Then another man entered upon him and said something similar to what the first man said, and he gave the same response. Then `Uthman (رضي الله عنه) said: Are they suggesting az-Zubair? He said: Yes. He said. By the One in whose hand is my soul, indeed he is the best among them as far as I know, and the most beloved of them to the Messenger of Allah (ﷺ) .

‘Abdullah told us: Suwaid told us: ` Ali bin Mus-hir told us similar report, with his isnad.
حَدَّثَنَا زَكَرِيَّا بْنُ عَدِيٍّ، حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، عَنْ أَبِيهِ، عَنْ مَرْوَانَ، وَمَا إِخَالُهُ يُتَّهَمُ عَلَيْنَا قَالَ أَصَابَ عُثْمَانَ رَضِيَ اللَّهُ عَنْهُ رُعَافٌ سَنَةَ الرُّعَافِ حَتَّى تَخَلَّفَ عَنْ الْحَجِّ وَأَوْصَى فَدَخَلَ عَلَيْهِ رَجُلٌ مِنْ قُرَيْشٍ فَقَالَ اسْتَخْلِفْ قَالَ وَقَالُوهُ قَالَ نَعَمْ قَالَ مَنْ هُوَ قَالَ فَسَكَتَ قَالَ ثُمَّ دَخَلَ عَلَيْهِ رَجُلٌ آخَرُ فَقَالَ لَهُ مِثْلَ مَا قَالَ لَهُ الْأَوَّلُ وَرَدَّ عَلَيْهِ نَحْوَ ذَلِكَ قَالَ فَقَالَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ قَالُوا الزُّبَيْرَ قَالَ نَعَمْ قَالَ أَمَا وَالَّذِي نَفْسِي بِيَدِهِ إِنْ كَانَ لَخَيْرَهُمْ مَا عَلِمْتُ وَأَحَبَّهُمْ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ حَدَّثَنَا عَبْد اللَّهِ حَدَّثَنَاه سُوَيْدٌ حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ بِإِسْنَادِهِ مِثْلَهُ‏.‏