פירוש על עבודה זרה 93:21

If one shared a wall with an idolatrous shrine, meaning his house was next to this shrine, he need not tear down his house and move somewhere else. Since he lived there before the shrine was built he does not need to move. However, if the house should fall down he may not rebuild the wall that will be shared with the shrine. What he may do is withdraw four cubits and build his own wall, one which will not be shared with the shrine.