modern construction would be superior and better, then he may be compelled, because in that case he suffers no harm.

If he says, “The mud bricks belong to me. How can you take them and demolish them?” we say to him: “We have only moved them to something better, and you suffer no harm. The expense is not yours, and the wall remains jointly owned. So what harm is there in that? You are refusing for no reason other than to spite your neighbour.”

But if he says, “I do not wish to spite him. Rather, when it was made of mud, I could drive pegs into the wall, whereas now I cannot,” this may constitute a valid purpose. For example, he may be someone who washes clothes and wishes to place pegs in the wall in order to hang the clothes on them.

In summary, if he refuses for a valid reason, then we do not compel him. But if he refuses merely to spite his neighbour, then there should be neither harm nor reciprocating harm.

His statement, “or it is feared that it may cause harm,” refers to a wall that has cracks and is feared to collapse. If the cracks run horizontally, then it is feared; but if the cracks run vertically, it is not feared. This applies to mud-brick houses. As for reinforced-concrete houses, it appears that all such cracks are defects, though horizontal cracks are more dangerous—unless there is a beam above, in which case it apparently has no effect. Thus, if the wall is feared to collapse, then, if one of them asks the other to rebuild it, he may be compelled to do so.

His statement, “The same applies to a river,” means that if there is a river between their lands—for example, a water channel is opened from the main river through which water flows, and that channel falls into disrepair—