Hilal bin Yasaf هلال بن يساف · The Book of Purification

"When you clean yourselves (with stones, after defecating), use an odd number."

"When you perform Wudu', sniff water in your nose and blow it out, and when you use small stones (to remove filth), then make it off (numbered)."

"The Messenger of Allah (ﷺ) saw some people whose heels were still dry, so he said: 'Woe to the heels from the Fire. Perform Wudu' properly.'"

"The Messenger of Allah (ﷺ) said: 'Do Wudu' properly.'" 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."