The Prophet (peace and blessings be upon him) said:
"Whoever performs ablution, let him blow out his nose; and whoever cleans himself with stones after relieving himself, let him use an odd number."
Hadith Referenceصحیح الجامع الصغیر / حرف الميم / 6171
Hadith Gradingالألبانی:صحيح
Hadith Takhrij[حم ق ن هـ] عن أبي هريرة [م] عن أبي سعيد. المشكاة ٣٤١.