An unfair acquisition or using without any reason has been accepted as a new source of commitment. In foreign law and in the Romeo- Germanic system it was positioned beside contract and civil responsibility of fault. This rule that nobody can be prosperous on another's loss had been a moral rule that find its way in the legal system. The entrance of this rule into the legal system was due to the lack of specific solution in the quarrels that occurs between demanding and demanded. And the demanded hasn’t done any fault but it was unfairly on the loss of wealthy demanding. The moral and fair foundation of this rule caused this rule to be accepted in most of the legal systems. Although In Egyptian and Iranian law there is no source for accepting this rule but for confirmation of this law some lawyers have used the foreign and Islamic Law. By studying and applying a comparative analysis of this rule in Iran and Egypt in a historical framework and also of its foundation which is an independent organization and the consequences of this rule we can understand that it has been coined for the sake of bridging the gap of legal rights in the Romeo- Germanic system.