What is the ruling on taking tips without the shop owner's knowledge, and what is the ruling on spending them in the causes of good?

Question:
What is the ruling in the religion regarding the extra money given to a worker by some of the customers, known as tips? What is the ruling on taking this money without the knowledge of the commercial shop owner? What is the ruling on spending this money in the causes of good? And is this considered one of the matters that the Prophet (peace and blessings be upon him) condemned when he asked that Companion, "Where did you get this from?" May Allah reward you with good.

Answer:
The worker in the store, or elsewhere, or in the factory, or in any other establishment that people visit to buy goods or manufactured items, must be truthful in his dealings with people. It is not permissible for him to take any money from the customers or clients; rather, he is limited to his salary or his share from the shop owner. Nothing is lawful for him except his salary or his share from the shop owner. It is not permissible for him to take anything from the customers, because if he takes something from the customers, this causes manipulation in buying and selling. He may betray the shop owner and be lenient with the customers because of this excitement or this gift that the customer gives him. He becomes lenient with the one who pays him from among the customers and strict with the one who does not pay him from among the other customers. This causes harm to the customers and betrayal of the shop owner. Therefore, it is obligatory for the worker to limit himself to his wages, to be truthful in his dealings with people, and to follow the system that the owner or the shop operates by, if this system does not conflict with the Islamic ruling. Yes. May Allah reward you with good, and may Allah reward you.