The obligation upon an oppressor:
The one who oppresses others should fear Allah and beware of transgression, because it will be counted as multiples of transgressions on the Day of Resurrection: one for him disobeying Allah, another for him oppressing his fellow Muslim, and a third for initiating and opening the gate of transgression and oppression for others to imitate. The wronged person could even eventually die as a result of the oppression, and the transgressor would bear the consequences of this.
Just look at what ‘Umar did with the public property of the Muslims: Aslam narrated: “`Umar Ibn Al-Khattaab appointed a freed slave of his, called Hunayy, as manager of the Himaa (i.e. a pasture devoted for grazing the animals of the Zakah or other specified animals, such as those used for Jihaad etc.). He said to him: 'O Hunayy! Do not oppress the Muslims and (be sure to) ward off their curse (i.e. invocations against you), for the invocation of the oppressed is responded to (by Allah); allow the shepherd having a few camels and those having a few sheep (to graze their animals in that land), and take care not to allow the livestock of 'Abdur-Rahman Ibn 'Awf and the livestock of 'Uthman Ibn 'Affan (to graze their animals in your land), for if their livestock should perish, then they still have their farms and gardens, while for those who own only a few camels or sheep, if their livestock should perish, they would bring their dependents to me and appeal for help saying: 'O Chief of the Believers! O Chief of the Believers!' Would I then neglect them? (No, of course not). So I find it easier to let them have water and grass than to give them gold and silver (from the Muslim treasury). By Allah! These people think that I have been unjust to them. This is their land, and during the pre-lslamic period, they fought for it but then they embraced Islam (willingly) while it was in their possession. I swear By Him in whose Hand my life is! Were it not for the animals (in my custody) which I give to be ridden for Jihaad (i.e. fighting in Allah's Cause), I would not have turned even a span of their land into a Himaa.'” [Al-Bukhari]
This was said regarding a matter that was not personal and he was merely being careful not to utilise the Muslim property in an incorrect manner, and yet he feared being unjust in any way. Therefore, those who transgress other people’s rights should fear Allah and fear the oppressed supplicating against them, as this is a very dangerous matter.
Mu`ath reported that the Messenger of Allah dispatched him (as governor of Yemen) and instructed him thus: “Beware of the supplication of the oppressed, for there is no barrier between it and Allah.” [Al-Bukhari and Muslim]
In another narration, the Prophet of Allah said: "There are three persons whose supplications are never rejected: The just leader, the fasting person when he breaks his fast, and the oppressed when he supplicates and whose supplication is raised above the clouds and the gates of heaven are opened for it, and (to whom) Allah will say: 'By My Glory! I shall assist you, even if it is after a while.'" [At-Tirmithi]
Abu Hurayrah reported that the Prophet said: “He who has done a wrong that affects his brother's honour or anything else, let him ask his forgiveness today before the time (i.e., the Day of Resurrection) when he will have neither a Deenaar nor a Dirham. (On that Day), if he has done some good deeds, a portion equal to his wrongdoings will be subtracted from them; but if he has no good deeds, he will be burdened with the evil deeds of the one he had wronged in the same proportion.” [Al-Bukhari]
Abu Hurayrah reported: “The Messenger of Allah said: “Do you know who is the bankrupt one?” The people said: ‘The bankrupt among us is the one who has neither money nor property.’ He said: “The real bankrupt one of my nation would be he who would come on the Day of Resurrection having (performed) prayers, (observed) fasting and (spent in) charity, (but he will find himself bankrupt on that Day due to depleting these good deeds) because he despised others, uttered slanderous terms against others, unlawfully devoured the wealth of others, shed the blood of others, and beat others. Therefore his good deeds would be credited to the account of those (who suffered at his hand). If his good deeds are exhausted, their sins (i.e., those he oppressed) will be entered in his account and he will be thrown into the (Hell) Fire.” [Muslim]
The transgressor must return the rights of people to them or their equivalent:
How can the transgressor free himself from his transgression? Imam As-Safareeni said: “The rights of people are either of a type that can be compensated for by an equivalent, like wealth or ruined goods, or by a type that cannot be compensated for.” This means that if a person has unjustly taken wealth, then he should return it; if he ruined something, then he should replace it; if he took something and used it, then he should return it and compensate the owner for the usage. These steps should all be accompanied with sincere repentance to Allah.
That is in the case of it being something that can be compensated for, but what should the transgressor do in the case that it is of the other type, which cannot be compensated for? Slandering a person or backbiting him are not things that can be compensated for, and in such a case one should first of all regret what he did and repent, then he should supplicate for the forgiveness of the one whom he slandered or backbit. If the person falsely accused another of adultery or fornication, then he should go back and inform those in front of whom he made the accusation that he was lying.
Furthermore, he should seek the pardon of the wronged person unless he knows that by informing him things would only get worse, in which case he should refrain from telling him and simply supplicate earnestly to Allah for the wronged person's forgiveness; he should also praise the wronged person in front of those same people that he had defamed or slandered him.
Ibn Taymiyyah said: “If what was taken is of the type that can be compensated for, then one must return it, and if the owner has died then he should return it to his heirs. In addition to this, he must supplicate for the deceased, because he had deprived him of his right to benefit from his property for the period he was alive in, during which the property was in the possession of the transgressor.”
How should people deal with the transgressor and the transgressed:
After knowing the positions of the transgressor and the transgressed against, we need to know the stance that people should adopt towards each of them.
Anas reported: “The Messenger of Allah said: 'Help your brother, whether he is an oppressor or is oppressed.' A man asked: 'O Messenger of Allah! I (know how to) help him when he is oppressed, but how can I help him when he is an oppressor?' He said: 'You can restrain him from committing oppression. That will be your help to him.'” [Al-Bukhari and Muslim]
Al-Baraa’ reported: “The Messenger of Allah commanded us with seven things (one of which is): “Support the transgressed.”
Ibn `Umar and his father, reported that the Messenger of Allah said: “A Muslim is a brother of another Muslim. (So) he should not oppress him, nor should he forsake him (i.e. when he is being oppressed).” [Al-Bukhari and Muslim]
Therefore, one must support the oppressed and the one who is being transgressed against; the one who refrains from supporting an oppressed person, whilst being able to, is sinful.
Abu Bakr said: “O people! You recite this verse (which means): “O you who believe! Upon you is [responsibility for] yourselves. Those who have gone astray will not harm you when you have been guided...” [Quran 5:105] (but misinterpret it) for I have heard the Messenger of Allah saying: 'When people see an oppressor but do not prevent him from (doing evil), it is likely that Allah will punish them all.'” [Abu Daawood and At-Tirmithi]
One should prevent the oppressor physically if possible, and this responsibility is greater with respect to the rulers and those in authority. If one cannot stop the oppressor physically, then he should do it verbally.
An oppressor must not be assisted:
Helping an oppressor is from the gravest of disasters; people should not imitate an oppressor and must prevent him and make him realise the wrong that he is doing; if people assist the oppressor then they will not get to drink from the fountain of the Prophet as He himself informed us of this being the case.
Some people support a transgressor because he is a relative or a fellow tribe member, but the Prophet warned against such oppressive behavior.
A believer should not be deceived:
All that has been mentioned thus far does not suggest that one should be easily deceived by someone who claims to have been oppressed, for it is not necessarily true that every person who claims to have been oppressed has actually been; the following is a case in point:
During the era of Abu Bakr a man whose hand and foot had been amputated came to Al-Madeenah from Yemen and went to Abu Bakr complaining that the governor there had wronged him. A few days later, a necklace of Asmaa’ Bint ‘Umays the wife of Abu Bakr was stolen and so people began searching for it. The Yemeni amputee assisted in the search and supplicated: “O Allah! Punish the one who stole from this righteous household.” Finally the necklace was found in a jewellery store. After investigating the matter, the jeweller claimed that the man from Yemen was the one who brought it to him, and when he was questioned he confessed to his crime. Therefore, Abu Bakr commanded that his other hand be amputated and said: “I swear by Allah! His supplication against himself was worse than his theft.” Although this man claimed that he had been oppressed, it was subsequently discovered that he had not been, and that his hand and foot were in fact rightfully amputated.