Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Messenger of Allah, peace and blessings be upon him, said: "When a person applies kohl, he should apply it an odd number of times, and when a person performs istinja with stones, he should also use an odd number (of stones) for istinja."

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) used to apply kohl three times in the right eye and two times in the left eye.

It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) would apply kohl with an odd number (of strokes).