Although cupping is most always beneficial, it is traditionally considered to be more effective at certain times of the month than at others. It’s generally not advised around the time of the New (full) Moon, because the humors are too compacted. The best time for cupping is generally considered to be around the middle of the lunar month, when the moon is large and full of light, because the humors are more expansive and exuberant at this time. The best time of all for cupping is considered to be around the 17th or 19th days of the lunar month, just about 2 to 3 days after the Full Moon. Some commentators (muhaddith) on the tradition (hadeeth) of the Messenger of God (Muhammad upon whom be the Peace and Blessing of God) explain that on those days the full moon has a gravitational impact on many things on earth. For example, the sea has high tides due to the full moon. Similarly, the flowing of the blood is also affected and flows faster during the full moon. One may loose much blood in these days if one undergoes cupping. Therefore, the Messenger of God (Muhammad upon whom be the Peace and Blessing of God) advised that one should undergo cupping on the 17, 19 and 21 of the lunar month. (Mishkat p. 389). Rasulullah (Sallallaahu alayhi Wasallam) advised that cupping should not be done on a Tuesday, since there is a certain time on a Tuesday that flowing blood does not stop. (Mishkat p. 389). Rasulullah (Sallallaahu alayhi Wasallam) also advised that cupping should not be done on Saturdays and Wednesdays as this could lead to leprosy. (Mishkat p. 389). As the need may arise, cupping may be performed at any time according to the condition or urgency.
Abu Hurairah (May God be pleased with him) reported that the Messenger (Muhammad upon whom be the Peace and Blessing of God) said, “Whoever performs cupping (hijaamah) on the 17th, 19th or 21st day (of the Islamic, lunar month) then it is a cure for every disease.” [Saheeh Sunan abi Dawud (3861)].
The best time of day to cup is generally considered to be the three hours following Sunrise, or the second half of the Sanguine period, when the blood is waxing exuberant. Cupping should not be done after bathing, except if the blood is unduly thickened; then, do it about an hour after bathing.