(Defenders of the Faith: A Guidebook to Clerics and Paladins variant, p. 79)
You have the supernatural ability to force possessing spirits out of the bodies they inhabit. You make a Charisma check (1d20 + your Charisma modifier) and consult Table 8-16, page 140 of the Player's Handbook, using your prestige class level plus your cleric level, if any, plus your paladin level -2, if any. If the result from the table is at least equal to the HD of the possessing creature, you force it out of the body. If the spirit belongs to a spellcaster using magic jar, the spirit returns to the receptacle. If it is a ghost, it becomes ethereal and free-floating again. In any case, the spirit cannot attempt to possess the same victim again for one day.