Silsilah as-Sahihah 446 — Rulings of using stones for Istinja

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Noble Prophet (peace and blessings of Allah be upon him) said: "When any person performs istinja (cleansing) with stones, he should use an odd number of stones, and when he blows his nose, he should also do so an odd number of times."