Is the thief absolved if the person whose property was stolen forgives him for part of the stolen money, and the thief returns another part, while a third part remains unreturned?

If the rightful owner, by his own choice, forgives the thief for the remaining stolen amount, then the thief's liability is absolved. He must then fulfill the conditions of repentance: regretting the theft, abandoning it, and resolving not to return to it.