Musnad Ahmad 402
It was narrated that Ibn Harmalah said:
I heard Sa`eed [i.e., Ibn al-Musayyabi] say: `Uthman (رضي الله عنه) went out for Hajj, then when he was partway there, it was said to `Ali {رضي الله عنه): He (`Uthman] has forbidden tamattu` [doing `Umrah then exiting ihram until Hajj]. `Ali (رضي الله عنه) said to his companions. When he sets out, set out too. And ‘Ali and his companions entered ihram with the intention of doing `umrah and `Uthman (رضي الله عنه) did not say anything to him about that ‘Ali (رضي الله عنه) said to him: Have I not been told that you forbade tamattu` by doing `umrah first? He said. Of course. ‘Ali said: Did you not hear that the Messenger of Allah (ﷺ) did tamattu’?`Uthman said: Of course,
حَدَّثَنَا يَحْيَى، عَنِ ابْنِ حَرْمَلَةَ، قَالَ سَمِعْتُ سَعِيدًا يَعْنِي ابْنَ الْمُسَيَّبِ، قَالَ خَرَجَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ حَاجًّا حَتَّى إِذَا كَانَ بِبَعْضِ الطَّرِيقِ قِيلَ لِعَلِيٍّ رِضْوَانُ اللَّهِ عَلَيْهِمَا إِنَّهُ قَدْ نَهَى عَنْ التَّمَتُّعِ بِالْعُمْرَةِ إِلَى الْحَجِّ فَقَالَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ لِأَصْحَابِهِ إِذَا ارْتَحَلَ فَارْتَحِلُوا فَأَهَلَّ عَلِيٌّ وَأَصْحَابُهُ بِعُمْرَةٍ فَلَمْ يُكَلِّمْهُ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ فِي ذَلِكَ فَقَالَ لَهُ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ أَلَمْ أُخْبَرْ أَنَّكَ نَهَيْتَ عَنْ التَّمَتُّعِ بِالْعُمْرَةِ قَالَ فَقَالَ بَلَى قَالَ فَلَمْ تَسْمَعْ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ تَمَتَّعَ قَالَ بَلَى‏.‏