What is the ruling on the prayer of someone who has a "fistula" from which blood and pus intermittently emerge and fall onto his undergarments, while he is harmed by covering the site of the fistula with cotton? And what is the ruling on his leading the prayer in this state?

If the bandage causes discomfort to the worshiper, he may pray according to his condition. He must wash off impurities and guard against them as much as possible, and wash clothes affected by them or change them for prayer. Whatever stains the garment after taking precautions is excused. One who suffers from a fistula or a bleeding wound is like a woman with post-natal bleeding (mustahadha) in the obligation to wash off the blood for each obligatory prayer and to tie a bandage on the wound. The imamate of one with an excuse is a matter of scholarly disagreement, and the preponderant opinion is that it is valid. However, if the excuse ceases and the body and clothes are pure, there is no impediment to leading the prayer if its conditions are met.