Certain sins are of such a nature that Taubah alone does not suffice and Qaza becomes obligatory. For example, a person did not perform his Salaah. (It is essential that together with making Taubah he performs the Qaza of the missed Salaah). Not performing Qaza and merely saying:
“O Allah forgive me. I have not performed my Salaah. I will perform it in future,” is definitely inadequate.
It is absolutely incumbent on that person to perform Qaza of the Salaah omitted. (Then only will the Taubah be accepted.)
Similarly, if a person did not pay his Zakaat, for his Taubah to be accepted, he will have to discharge the outstanding amount. Without paying out the due zakaat, it will also not suffice for him to say, “O Allah, forgive me, I will give out my zakaat in future.”
The crux of the matter is that those laws of the Shariat which can be recompensed by making qaza, and Shariat has made its qaza obligatory, the acceptance of taubah requires that we fulfil the qaza as well as beg forgiveness for not having fulfilled the obligation at its prescribed time.
The similitude to this situation is where one is in debt or has to pay a government tax at a stipulated date but missed the deadline. He presents himself before the magistrate and begs for leniency saying: “I did not pay my tax on time, please forgive me, I am begging your forgiveness.”
It is possible that he may be pardoned for not meeting the deadline but does this mean that he will be absolved from paying the outstanding tax as well? Definitely not! The tax will still have to be paid out.
As far as the violation of the rights of human beings is concerned, the dictates of taubah require that the particular right (which was usurped) be fulfilled. For example, a person usurped another’s wealth. “I beg your forgiveness,” he wails. “Please forgive me, I have taken your wealth.”
This is insufficient. He is required to first pay out the wealth that he owes and then seeks the victim’s forgiveness.
~ Taken from the Discourses of Mufti Mahmood al-Hasan Gangohi RA ~