What is the ruling on the prayer of one who suffers from the discharge of remnants of a hemorrhoid operation, and is it obligatory for him to renew his ablution and change his clothes for every prayer?

If blood is flowing continuously, clean the area and bandage it. Perform ablution (wudu') for each prayer after its time has begun, and pray the obligatory prayer and as many supererogatory prayers as you wish. However, if the blood stops for a period sufficient for purification and prayer, then delay the prayer and purification until that period. You must make up any prayers you missed due to illness.