The Prophet ﷺ said: "Whoever has wronged his brother in his honour or anything else, let him settle it with him today, before there are no dinars and no dirhams," and he described the bankrupt person as one whose good deeds are handed over to those he wronged. When the person is dead or untraceable, the scholars say the obligation does not simply vanish: return stolen or owed property to their heirs if they can be identified, and if that is impossible, give it away in charity on the wronged person's behalf, intending its reward for them — this is the position of many scholars, including Ibn Taymiyyah and Ibn al-Qayyim. For wrongs that cannot be repaid in property, such as backbiting a person now deceased, repent sincerely to Allah, ask forgiveness for them abundantly, and do good on their behalf, hoping Allah will satisfy them on the Day of Judgement from His bounty.
Q&A · Repentance & Sin
I wronged someone who has since died, or whom I can no longer find — how do I put it right?
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.