What is the ruling of Islamic law regarding deducting a large portion of the wages of a worker who was entrusted with plastering work and pledged to perfect it, but completed it with very poor quality, given that he was supported with expensive raw materials, and despite being warned about his mistakes at the beginning, he justified the poor work by blaming his assistant? Is it permissible to deduct the value of the damages incurred by the building and the value of the raw materials?

This worker is a joint employee, deserving wages upon completion of the agreed-upon work in the agreed-upon manner. If he falls short, the hirer has the right to deduct an amount corresponding to the deficiency in the work, which should be determined by experts.

If the experts rule that the deficiency or defect in the worker's labor is equal to the deducted amount, then there is no blame on the questioner. However, if the amount is greater than the value of the deficiency, then the questioner must return the difference to the worker.