Article 198 of Civil Code

If, after the contract has been concluded and before its performance has been completed, exceptional circumstances of a general nature arise which could not have been foreseen at the time of its conclusion, and their occurrence results in the performance of the obligation arising from it, although not becoming impossible, becoming onerous for the debtor, so as to threaten him with a grave loss, the judge may, after balancing the interests of both parties, reduce the onerous obligation to a reasonable level by narrowing its scope or increasing the consideration for it. Any agreement to the contrary shall be void.