What is the basis for obligating both rent and compensation for diminution in cases of usurpation?

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Both the obligation of rent and the obligation of compensation for diminution are established independently. Therefore, when they coincide, both become obligatory. This is analogous to an item that is retained for a period and then destroyed; both the rent for retention and the compensation for total loss become due. Rent is due in exchange for the forfeited use/benefits (*manafi'*), not in exchange for the physical parts, which is why rent is obligatory even if no physical parts are lost.