Restitution is making things right. Justice must be done. It's in the Bible, Exodus 22:9, TLB. "In every case in which an ox, donkey, sheep, clothing, or anything else is lost, and the owner believes he has found it in the possession of someone else who denies it, both parties to the dispute shall come before God for a decision, and the one who God declares guilty shall pay double to the other."
We sin against God by cheating our fellow men. It's in the Bible, Leviticus 6:2-5, TLB. "If anyone sins against Me by refusing to return a deposit on something borrowed or rented, or by refusing to return something entrusted to him, or by robbery, or by oppressing his neighbor, or by finding a lost article and lying about it, swearing that he doesn't have it—on the day he is found guilty of any such sin, he shall restore what he took, adding a 20 percent fine, and give it to the one he has harmed; and on the same day he shall bring his guilt offering to the Tabernacle."
God requires confession as well as repayment for wrongs. It's in the Bible, Numbers 5:5-7, NIV. "The Lord said to Moses, 'Say to the Israelites: 'When a man or woman wrongs another in any way and so is unfaithful to the Lord, that person is guilty and must confess the sin he has committed. He must make full restitution for his wrong, add one fifth to it and give it all to the person he has wronged.'"