Hadithcore
Musnad Ahmad, 404
sahih· Darussalam

It was narrated from Abu Anas that `Uthman (رضي الله عنه) did wudoo` in al-Maqa`id, washing each part of the body three times. Some of the Companions of the Messenger of Allah (ﷺ) were with him. He said:

Didn`t you see the Messenger of Allah (ﷺ) do wudoo like this? They said: Yes

حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا سُفْيَانُ، عَنْ أَبِي النَّضْرِ، عَنْ أَبُو أَنَسٍ، أَنَّ عُثْمَانَ، رَضِيَ اللَّهُ عَنْهُ تَوَضَّأَ بِالْمَقَاعِدِ ثَلَاثًا ثَلَاثًا وَعِنْدَهُ رِجَالٌ مِنْ أَصْحَابِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ أَلَيْسَ هَكَذَا رَأَيْتُمْ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَتَوَضَّأُ قَالُوا نَعَمْ‏.‏

References1 variant
In-Book Reference
Book 4, Hadith 6