What is the ruling on deducting three days' pay from an employee's salary if they are absent for one day without a valid excuse?

This contract is permissible and can be interpreted as a penalty clause if the compensation is equal to the actual damage, or as a matter of fluctuating wages according to the agreement. So, if the worker consistently performs in a certain manner, he receives a specific wage, and if his work decreases, the wage decreases proportionally to that reduction. Evidence for its permissibility is what Ibn al-Qayyim mentioned, that Omar ibn al-Khattab, may Allah be pleased with him, dealt with people such that their wages varied according to who brought the seeds.