Is a land lease contract valid if it stipulates that the tenant may leave the crop until it matures, despite the agreed-upon short term?

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If the contract stipulates that the crop must remain on the land until it matures, the contract is void (*fasid*). This is because the stipulation combines two contradictory elements: defining a term implies vacating it, whereas stipulating retention contradicts this. Furthermore, the duration of this retention period is unknown (unspecified).