What is the meaning of the Hadith: "And if you use pebbles (for purification), then use an odd number"?

The meaning of the Prophet's (peace be upon him) saying: "Let him use an odd number" regarding istijmar (cleaning oneself with stones after defecation) is that the number of cleansing stones should be odd, such as three, five, or seven. If cleanliness is not achieved with the smaller number, one should increase it.

Istijmar is the removal of impurities from the private parts using small stones.