Is it permissible for a butcher to pray in his professional uniform?
20-1-2014 | IslamWeb
Question:
Is blood considered Najaasah (ritual impurity)? In other words, is it permissible for a butcher to pray in the same clothes that he wears for slaughtering, which have some blood on them?
May Allaah reward you.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Blood is Najasaah (ritually impure) according to most Muslim scholars. In his interpretation of {blood}, in the verse that means {Prohibited to you are dead animals, blood, the flesh of swine, and that which has been dedicated to other than Allaah…}[Quran 5:3], Imaam Al-Qurtubi 
said:
As regards what Allaah says, scholars agree that blood is ritually impure and is forbidden from being consumed or utilized. Ibn Khuwayz Mindaad said that blood is unlawful unless it is found on the flesh and inside arteries, in which case using it may be forgiven. It is permissible to pray with a small amount of blood on the body.
However, you should note that the blood that flows from slaughtered animals attaches impurity to the part of the clothes or the body which it soils, because Allaah Almighty Says (what means): {Say, “I do not find within that which was revealed to me [anything] forbidden to one who would eat it unless it be a dead animal or blood spilled out…”}[Quran 6:145] Dr. Wahbah Az-Zuhayli said:
‘The spilled out blood’ is the blood that pours and flows in the arteries of the slaughtered animal, which indicates that what is forbidden is liquid blood. Ibn ‘Abbaas 
said, "The verse refers to the blood that comes out of living animals and out of arteries when slaughtering. Excluded, however, are the coagulated blood-formed organs; such as the liver and the spleen, the blood that soils the flesh of the part at which the animal is slaughtered, and the blood that remains in the arteries, because such blood is not liquid.”
Consequently, if much liquid blood soils your clothes because of slaughtering, then you must not pray in such clothes except after washing the soiled part. If the blood that soils your clothes has mixed with the flesh of the slaughtered animal or was in the arteries, then it does not make your clothes ritually impure, and thus you may pray in them. Our advice is that you should put on a clean garment whenever you want to pray.