How can a person who repented after stealing money from people in the market and from his colleague in the grocery store return it, when he does not remember how much he stole and does not know the rightful owners, and what should he do if he is poor?

Theft is a grave sin and a despicable act, and Allah has prescribed repentance for it. For repentance to be sincere (tawbah nasuha), five conditions must be met: sincerity, abstaining from the sin, regretting having committed it, resolving never to return to it, and that repentance must occur before the death rattle (ghargarah). In addition, the stolen items must be returned to their owners; if the owners cannot be identified, their value should be given as charity. He should also increase his good deeds as a form of compensation.