The Messenger of Allah (s) says:
“A repentant person is like one who has no sin.”1
Allah, the Most High, sent us prophets in order to clarify the right path and explain what is lawful (halal), what is permitted for us to do, and what is forbidden (haram) and harmful which we should avoid, such as lying, murdering, gambling, stealing, being deceitful, being undutiful towards parents, and other forbidden acts. Also he instructed us on what is obligatory (wajib) for us to perform such as prayer, fasting, helping the poor, respecting Prophet Muhammad (s) and his holy progeny (Ahlul-Bait) (peace be upon them all) and so on.
Some people deliberately disobey Allah and His orders which are beneficial for mankind and the welfare of the society. They do the forbidden such as stealing another's property or oppressing people or doing harm to their parents, or giving up their duties which Allah made obligatory, like paying poor-rates (zakat) for the needy, not performing prayers, and behaving badly towards their parents.
For whoever stops doing an obligatory duty or commits a forbidden act, it is obligatory for him to repent, take responsibility for his action and ask forgiveness from Allah by regretting the mistake. If someone oppresses people or takes their property unlawfully, then that person should apologise to them and return their rights so that Allah is pleased with him.
Surely, Allah is Most-Merciful to His servants; therefore He accepts their repentance and forgives them if they regret for their evil deeds and want to make righteous people out of themselves again.
The Messenger Muhammad (s) says: Surely, Allah is Oft-Pardoning and Most-Merciful, Who forgives His servants' sins if they ask forgiveness and give them up, as if they had not committed any sin.
Thus, repentance purifies the self from sin as water purifies clothes from dirt.
Among the rights of Allah is to punish the disobedient and not accept their repentance but He is Most-Merciful with His servants and loves to help them by giving them opportunities to think and repent in order to set them on the right path towards reforming themselves and society.
Thus, repentance is “Giving up disobedience without repeating it again”
1. Disobedience is to commit forbidden acts and give up obligatory ones.
2. Repentance is to give up disobedience and refrain from repeating it.
3. Allah is Most-Merciful with His servants. He accepts their repentance and forgives them if they regret their misdeeds.
4. It is obligatory for a man to ask Allah for forgiveness and to do the obligatory acts and give up the forbidden ones, and to regret his evil deeds.
Praise be to Allah, Lord of the worlds.