Question: A man bought a piece of land from another man, and the buyer built a wall around it. Then a third man, known for frequent quarrelling and disputation, came and claimed to the buyer that he has a share in this land. The seller had already guaranteed to the buyer whatever might be deficient or invalid, and so on. Is the buyer obliged to open for himself, over this land, the door of quarrel and dispute before the judges, or is he not obliged to do that?
The answer: If the buyer knows, or thinks, that the claimant’s claim is invalid, and no indicatory circumstance appears to him that points to the validity of what the man claims – then he is not obliged to answer him. But if there appears to him something that points to the soundness of his demand, then it becomes obligatory for him to answer him.
Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2