"The Messenger of Allah ﷺ said: 'Do Wudu' properly.'" [1] [1] Isbighu Al-Wudu'. And this narration supports the claim that some of them used this expression to mean "three times" for each limb, rather than "properly." (Using translation from Nasāʾī 142)   

قَالَ رَسُولُ اللهِ ﷺ «أَسْبِغُوا الْوُضُوءَ»  

"We were sitting with 'Abdullah bin 'Abbas and he said: 'By Allah, the Messenger of Allah ﷺ did not say specifically anything for us above the people, except for three things: He commanded us to do Wudu' properly, [2] not to consume charity, and not to mate donkeys with horses.'" [1] Isbagh Al-Wudu' [2] An Nusbig Al-Wudu' (Using translation from Nasāʾī 141)  

وَاللهِ «مَا خَصَّنَا رَسُولُ اللهِ ﷺ بِشَيْءٍ دُونَ النَّاسِ إِلَّا ثَلَاثَةَ أَشْيَاءٍ فَإِنَّهُ أُمِرْنَا أَنْ نُسْبِغَ الْوُضُوءَ وَلَا نَأْكُلُ الصَّدَقَةَ وَلَا نُنْزِيَ الْحُمُرَ عَلَى الْخَيْلِ»