He works in a restaurant and takes tips with the knowledge of the owner

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Check below answers in case you are looking for other related questions:
Ruling on giving tips to plumbers, carpenters and phone company employees
Ruling on working as a baker in a restaurant that serves alcohol in a western country

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Ruling on giving tips to plumbers, carpenters and phone company employees
Ruling on working as a baker in a restaurant that serves alcohol in a western country

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