What is the ruling of the Shari'ah on the dispute between a worker and an engineer regarding three months' wages, given that the worker was unable to complete the agreed-upon project due to numerous modifications and harassments, and he refuses to return the wages, arguing that it was a monthly salary and not against the full completion of the project?

The contract is the law between the contracting parties, and your employer agreed with you not to cease working until the project is completed. Therefore, you are not permitted to leave the work before its completion except for a valid excuse. This is what the lease contract stipulates, and the condition further strengthens it. If your departure from work is not due to a valid excuse, then your employer has the right to seek compensation from you for any damage incurred, based on the saying of the Prophet, peace and blessings be upon him: "Muslims are bound by their conditions." And the saying of Shuraih Al-Qadhi: "Whoever imposes a condition upon himself willingly and without coercion is bound by it."