What is the ruling if one, who has a cut on the inside of his mouth, swallows blood during prayer?

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.

Swallowing blood from cuts in the mouth and tongue during prayer does not invalidate the prayer, if it was done unintentionally. In such a case, there is no harm in it and the prayer is valid. However, if the worshipper swallows blood intentionally, the prayer is invalid. If one swallows a very small amount of blood outside of prayer, there is no harm in it, whereas it is better to spit it out. If the amount of blood was significant, he is obliged to spit it out.

Allaah Knows best.