Is the money an employee takes from clients, under the pretext that his salary is insufficient, lawful or unlawful?

It is not permissible for an employee to accept gifts in their work because they are often bribes. They must return them to their owners. If they are unable to do so, they are not allowed to take them unless authorized by their employer, because such gifts to employees are considered embezzlement (ghulul), in accordance with the Prophet's (peace and blessings be upon him) saying: "Gifts to employees are embezzlement." And his saying: "What is wrong with a worker whom I send out, and he says: 'This is for you, and this was given to me as a gift'? Why did he not stay in his father's house or his mother's house to see if he would be given gifts or not? By Him in Whose Hand is Muhammad's soul, no one among you will take anything from it but he will come with it on the Day of Resurrection, carrying it on his neck."