Is it permissible to take a sum of money not exceeding five pounds, or to buy food for less than five pounds and keep the remainder, in order to buy food due to the employer not providing lunch for the worker or its delay, knowing that the monthly salary is not enough to cover the cost of buying food?

If the contract between you does not stipulate a lunch meal, and he provided it as a voluntary act, then it is not permissible to take anything from his money without his permission if the meal is delayed or does not arrive. However, if the contract stipulates his obligation to provide the lunch meal and the salary, then this is permissible according to the preferred view, and he must adhere to it. If he breaches this, you have the right to demand what you agreed upon or to seek his permission to take compensation for it, and it is not permissible to take it without his permission. Ibn Qudamah al-Hanbali permitted hiring a worker for his food and clothing, and this is the madhhab of Malik and Ishaq, and Abu Bakr, Umar, and Abu Musa, may Allah be pleased with them, did so.