It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When any of you performs ablution, let him put water into his nose, then blow it out, and let him use an odd number of stones."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 223