It was narrated that Qatadah said:

I heard `Abdullah bin Shaqeeq say: `Uthman (رضي الله عنه) forbade tamattu` and `Ali enjoined it. `Uthman (رضي الله عنه) said something and ‘Ali (رضي الله عنه) said to him, You know that the Messenger of Allah (ﷺ) did that. `Uthman (رضي الله عنه) said: Yes, but we were in a state of fear [at that time]. Shu`bah said: I said to Qatadah: What were they afraid of? He said: I do not know,

حَدَّثَنَا رَوْحٌ، حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، قَالَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ شَقِيقٍ، يَقُولُ كَانَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ يَنْهَى عَنْ الْمُتْعَةِ وَعَلِيٌّ رَضِيَ اللَّهُ عَنْهُ يُفْتِي بِهَا فَقَالَ لَهُ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ قَوْلًا فَقَالَ لَهُ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ لَقَدْ عَلِمْتَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَعَلَ ذَلِكَ قَالَ عُثْمَانُ رَضِيَ اللَّهُ عَنْهُ أَجَلْ وَلَكِنَّا كُنَّا خَائِفِينَ قَالَ شُعْبَةُ فَقُلْتُ لِقَتَادَةَ مَا كَانَ خَوْفُهُمْ قَالَ لَا أَدْرِي‏.‏