The ruling on a penalty clause when the employer delays the agreed-upon work for a specific period

Question : But here is a method some people use. They say: If the period ends and the work is not completed, you must pay a deduction of so much for each month or so much for each day. Is this permissible or not?

Answer : We see that this requires a distinction. If a period is set in which the work can reasonably be completed, there is no harm. However, if a period is set in which completing the work is considered rare, then it is not permissible, because it is a form of gambling.
Let me give you an example. Suppose I give a contractor a house and set the period at one year. A house like this can be built in a year with ease, without hardship. So I tell him: If the period ends and you have not finished the construction, you must pay a deduction. This is permissible and there is no harm in it, because the benefit of this deduction is that the work is completed within the set period. But if I told him to build this house for me in six months, and said: If the period ends, you must pay a deduction of so much for each day or so much for each month, then this is not permissible.
Because this is gambling. If I give it to him for a period of six months, his wage will be higher than if I gave it to him for a year. In that case, he will either be a gainer if he completes the work within the set period, or a loser if he does not complete the work within the set period. Therefore, this distinction is necessary. What is it? That if a period is set in which the work can be completed in the usual manner, then there is no harm in saying: If the period ends and the work is not completed, you must pay the deduction.
Because the wage will be customary and not high? It will be customary. But if a period is set in which the work cannot be completed except in a rare manner, then the wage must be increased. In that case, he will be either a gainer or a loser if he is delayed and a deduction is taken from him.