Is an accountant sinful for a mistake in calculating a patient’s bill that led to an overpayment which was not fully returned, and is it permissible for him to use another amount from a second patient’s dues to settle this error, knowing that he is new to the job?

The hospital must return the excess money mistakenly paid by the patient or seek their forgiveness. It is not permissible to take this money without their knowledge to pay the debt of another patient, as the financial liability of each patient is independent. The property of a Muslim person is not lawful unless given with their full consent, as Allah Almighty says: {O you who have believed, do not consume one another's wealth unjustly} (An-Nisa: 29). And as the Prophet, peace and blessings be upon him, said: "Indeed, your blood, your properties, and your honor are sacred to you..." and "The property of a person is not lawful except with their full consent," and "Every Muslim's blood, property, and honor are sacred to another Muslim," and "Whoever unlawfully takes a Muslim's property will meet Allah Almighty while He is angry with him."