Is it permissible to transfuse blood from a deceased person to a living person, or from a brain-dead person, or from a person on the verge of death?

Donating and receiving blood are not permissible except in cases of necessity to save a patient's life. There is no difference whether it is taken from a living person or a deceased person, except regarding permission. If the deceased person did not give permission, then their heir is the one who grants permission. If the person is unknown or has no heir, then the ruler (Wali al-Amr) undertakes this.

As for someone who is brain-dead, it is not permissible to transfer blood from them until cardiac death is confirmed, because brain death is not considered a legally recognized death according to the more preponderant opinion.