Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Donating the reward of fasting to the owner of the money does not suffice—he must either return what he took or the owner must waive the sum owed to him.
Answering your question, Dar Al-Ifta Al-Misriyyah, states:
It is established in Islamic law that rights owed to humans are not waived except by their observance or by exoneration.
Samra ibn Jundub narrated that the Messenger of Allah (peace be upon him) said: “A person remains indebted with what he took until he returns it” (Abu Dawud, At-Tirmidhi, ibn Majah and Ahmed. Al-Hakim declared it authentic.)
Donating the reward of fasting to the owner of the money does not suffice—he must either return what he took or the owner must waive the sum owed to him.
The conditions for repentance [for sins] concerning the rights of humans include:
1- Restitution of rights
2- Feeling regret for having committed the sin
3- Desisting from it
4- Resolving never to commit it again.
Almighty Allah knows best.
Source: http://www.dar-alifta.org/Foreign/ViewFatwa.aspx?ID=2857