When can a contract stipulate both a duration and the completion of a specific work?

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Stipulating both time duration and the completion of work is impermissible when the subject of the contract has work associated with it, like an animal whose benefits are measured by its labor, or when the subject is something without work, like a house or land, which must be contracted for a fixed duration. Abu Hanifa and Al-Shafi'i hold this view. This is because combining both elements introduces undue uncertainty (gharar). This uncertainty arises because the work might be finished before the period expires, meaning either the contractor overworks beyond the contract terms or abandons work during the remaining time. Furthermore, the work might not be finished within the stipulated time, forcing either the contractor to work beyond the term or the client to accept incomplete fulfillment of the contract.