Hijama means 'sucking' or to 'bring something to its normal state' and it is a Sunnah (tradition of Prophet Muhammad peace be upon him). The Prophet (peace be upon him) advised followers to carry out this healing act for better blood circulation.  

There are many Hadith on the Prophet recommending Hijama for Muslims and the entire humanity. There is a well-known saying of the Prophet: “There is cure in three substances; a drink of honey, incision with a knife used for Hijamah (cupping), and cauterizing by fire. And I forbid my Nation from cauterizing by fire.” 

Performing Hijama on any day, any time, any occasion is SUNNAH as per this Hadeeth.

There are some specific points in our body that which Prophet (PBUH) covered while doing Hijama, these points are called Hijama. There are 13/14 SUNNAH Points. Abu Hurairah(r.a) reported that the Messenger (PBUH) said, “Whoever performs cupping (Hijama) on the 17th, 19th or 21st day (of the Islamic, lunar month) then it is a cure for every disease.” [Sunan Abu Dawud Hadith No: 3861]. 

Sunnah Days of Hijama are the 17th, 19th, and 21st days of the Islamic/lunar month, specific days for the abovementioned Hadith. People are doing Hijama these days at certain points which the Prophet(PBUH) did during his life in the name of SUNNAH HIJAMA.