«كان إذا اكتحل اكتحل وترا وإذا استجمر استجمر وترا»
It was the practice of the Prophet (peace and blessings be upon him):
"When he (peace and blessings be upon him) applied kohl, he would apply it an odd number of times, and when he cleaned himself with stones (istijmar), he would do so an odd number of times."
Hadith Referenceصحیح الجامع الصغیر / حرف الكاف / 4680