Rulings of Prayer
Dress code: Part Five
One of the other necessary conditions for the clothes  that are worn during prayer is that they must not have been made with parts of the body of Maytah. In other words, the clothes in which one intends to perform their prayer must not have been made with the skin or other parts of the corpse of an animal whose blood gushes out and which has died, has been killed or has not been slaughtered based on the Islamic laws.
Also, if the person praying is wearing clothes made of parts of a corpse of an animal whose blood does not gush out such as a snake or a fish, according to obligatory precaution the prayer will still be invalid. 
However, parts of an animal's corpse which do not have a soul (such as the hair or fur of sheep) will not create a problem for the prayer. So, one is allowed to make clothes with the hair and fur of dead animals whose meat is Halal and perform prayers in them. But it is still impermissible to make clothes out of skin taken from the corpse of these animal.
Cow skin is an exception to this rule and praying with clothes made of cow leather is permitted  under the condition that one has purchased them from a Muslim market. In this case, even if one is unaware if the animal was slaughtered properly according to Islamic laws or not, they can still perform their prayers in those leather clothes.
Even if one does not know if the leather has been brought from Islamic countries or not, they can still perform their prayers in those clothes. But if one is certain that the leather used in their clothes is from non-Islamic countries or they are certain that the shop owner is an irresponsible person and has not done any research about the source of the leather, it will not be permissible for them to perform prayers in those clothes.