However...

However, if these things are obtained from a Muslim who himself obtained them from a non-Muslim and it is not known whether the animal in question was slaughtered according to Islamic law, it is prohibited to eat its meat or fat and it is also prohibited to use its hide for offering prayers.

Nevertheless, if these things are obtained from a bazaar of Muslims or from a Muslim and it is not known whether they were purchased earlier from a non-Muslim and the probability may be that the said Muslim made investigation in the matter, it is permissible to use its hide for offering prayers and also to eat that meat and fat, even though, in fact, the Muslim might have purchased these things from a non-Muslim. Blood 97.

The blood of a human being and of every animal whose blood gushes out when its great artery is cut is impure. The blood of a fish or a mosquito is pure because it does not gush. 98. If an animal whose meat is lawful to eat is slaughtered in accordance with the method prescribed by religious law and its blood comes out in the usual quantity, the blood, which is still left in its body is pure.

However, the blood which goes back into the body of the animal owing to its inhaling its breath, or on account of its head having been at a higher level at the time of its slaughtering, is impure. 99. If there is the slightest quantity of blood m the egg of a hen its we should be avoided m accordance with obligatory precaution. However, if the blood is m the yolk (yellow portion) of the egg its albumen (white portion) will be pure unless the veil lying between the yolk and the albumen is torn.

And m case a hole appears m the nail or the skin and it is difficult to take out blood and to purify that spot for the purpose of ablutions or ceremonial bath one should perform tayammum. (See Article 708). 103. If a person does not know whether blood has dried under the skin or the flesh has assumed such a shape owing to hurt, it is pure. 104.