Narrated Anas ibn Malik that the Messenger of Allah said: Whoever wants to be treated with Cupping let him search for the 17th or the 19th or the 21st. And do not let your blood become hyperaemic (becomes excessive/boil/ rage) so that it kills you.
Abu Hurairah that the Messenger of Allah said: Whoever gets treated with Cupping on the 17th and 19th and the 21st will be cured from every illness.
Narrated Anas ibn Malik that the Messenger of Allah said: Whoever wants to be treated with Cupping let him search for the 17th or the 19th or the 21st.
Many other narrations of the Prophet allude to the same three days of the Lunar month “17th, 19th and the 21st. Ibn al-Qayyim mentions the physicians in that time had reached a conclusion that Hijama is more beneficial in the beginning of the third quarter of the lunar month. Some of the theories revolved around the gravitational pull of the moon and its affects on bodily fluids. Ibn Sina believed that the blood becomes agitated around the latter part of the month. However Hijama can be performed at any time of the month if needed.