Sunan an-Nasa'i, Book 1, Hadith 143 (In-Book) ⓘ
It was narrated that 'Abdullah bin 'Amr said: "The Messenger of Allah 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."
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا جَرِيرٌ، عَنْ مَنْصُورٍ، عَنْ هِلاَلِ بْنِ يِسَافٍ، عَنْ أَبِي يَحْيَى، عَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَسْبِغُوا الْوُضُوءَ " .
also referenced under: Volume 1, Book 1, Hadith 142 (DarusSalam)