The Impurity of Blood and the Ruling on Praying with It

Question:
Is blood ritually impure? And if a person prays while there is a spot of blood on his garment, shirt, or trousers, does he have to repeat the prayer?

Answer:
Blood is ritually impure according to the school of a group of scholars, so the blood is washed off. The Prophet (peace and blessings be upon him) said to the woman who asked him about menstrual blood that gets on the garment:
He said: This is evidence that blood is washed off the garment. Among the conditions for the validity of the prayer is purity from ritual impurity (hadath), and purity from ritual impurity (najasah) in the garment, the body, and the place of prayer. If he did not know about the blood, he prays, and there is blood on his garment, and he did not know until after the prayer, then his prayer is valid. Or if he knew about it and forgot it, and he prayed, his prayer is valid. However, if he knew about the blood before the prayer, it is obligatory for him to wash it and remove it. Yes.