Is it permissible to embed a programmatic command that stops the software from working after a certain period without the client's knowledge, as a guarantee for the payment of the agreed-upon amount?

What the scholars deem more cautious and more absolving of responsibility in this matter is to inform the client about the programming command that prevents the utilization of the paid amount until it is removed. This is because there is a possibility that the programmer may not be available until the command is removed, which would cause the client to lose their right.

Therefore, if the programmer does not receive their fee until the command is removed, there is no blame upon them, provided they take precautions to ensure that the client's right is not lost during their lifetime or after their death.