Musnad Ahmad 1139
It was narrated from Marwan bin Al-Hakam that he said:
I saw `Ali and `Uthman (رضي الله عنهما) between Makkah and Madinah. `Uthman was telling people not to do tamattu` or join them together (Hajj and ‘Umrah, i.e., qiran). When `Ali (رضي الله عنه) saw that, he entered ihram for both of them together and said: Here I am for `Umrah and Hajj together ‘Uthman (رضي الله عنه) said: You see me telling the people not to do that and you do it? He said: I will not give up a Sunnah of the Messenger of Allah (ﷺ) for the opinion of anyone among the people.
حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنِ الْحَكَمِ، عَنْ عَلِيِّ بْنِ الْحُسَيْنِ، عَنْ مَرْوَانَ بْنِ الْحَكَمِ، أَنَّهُ قَالَ شَهِدْتُ عَلِيًّا وَعُثْمَانَ رَضِيَ اللَّهُ عَنْهُمَا بَيْنَ مَكَّةَ وَالْمَدِينَةِ وَعُثْمَانُ يَنْهَى عَنْ الْمُتْعَةِ وَأَنْ يُجْمَعَ بَيْنَهُمَا فَلَمَّا رَأَى ذَلِكَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ أَهَلَّ بِهِمَا فَقَالَ لَبَّيْكَ بِعُمْرَةٍ وَحَجٍّ مَعًا فَقَالَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ تَرَانِي أَنْهَى النَّاسَ عَنْهُ وَأَنْتَ تَفْعَلُهُ قَالَ لَمْ أَكُنْ أَدَعُ سُنَّةَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لِقَوْلِ أَحَدٍ مِنْ النَّاسِ‏.‏