Fiqh-us-Sunnah - 1.8

Hadith 1.8.1

Blood

This includes blood that pours forth from an animal's body, such as blood from a slaughtered animal, or from menstruation, except for what small amounts are overlooked. Ibn Juraij said about the Qur'anic verse "...or blood poured forth..." (al-An'am 145), that this is the blood that flows out. The blood that does not flow out, but remains in the veins, is permissible. This is related by Ibn al-Mundhir. And it is also related from Abu Majlizn in his discourse on blood that he was asked, "What about the blood that remains in the slaughtered sheep or at the top of the cooking pot?" He answered, "There is no problem with it. What is forbidden is the blood that flows out (of the animal at the time of slaughtering)." This was recorded by 'Abd ibn Hameed and by Abu ash-Shaikh. It is also related from 'Aishah that she said, "We used to eat the meat when the blood was streaking the pot." Al-Hassan said, "The Muslims always prayed, even while they were bleeding." This was mentioned by al-Bukhari. It is confirmed that 'Umar prayed while his wound was bleeding. Elucidating the point, Ibn Hajr says in Fath al-Bari (a commentary on Sahih al-Bukhari): "Abu Hurairah did not see anything wrong in a drop or two of blood during the prayers. Based on this report from Abu Hurairah, the blood of a flee or the blood that comes from a pimple are to be overlooked.
Abu Majlizn was asked about pus that gets on the body or the clothes. He said, 'There is nothing wrong with them.
Allah mentions only the blood, not the pus."' Commenting on the subject, Ibn Taimiyyah says, "It is obligatory to clean the clothes from pus, purulent matter or similar fluids." He also says, "There is no proof concerning its impurity." It is preferred for the person to avoid contact as much as possible with these substances.