Oppression is, indeed, the most hateful practice a human being may follow. It is degrading to the one who commits it and to the one at the receiving end of it. It is for this reason that Islam stresses in a variety of methods the importance of justice.
The Holy Prophet (sallal laahu alaihi wasallam) lists seven groups of people who will have Allah’s Shelter on the Day of Judgment. The first of these is a just ruler. With such emphasis, it is not surprising that Islamic history has known a long chain of fair-minded rulers.
The Holy Quraan says: Wrong not, and you shall not be wronged. (2:279) Sayyiduna Rasoolullah (sallal laahu alaihi wasallam) said: Oppression is the darkness on the Day of Resurrection. (Bukhari & Muslim) This means that the oppressor will face severe torments on the Day of Judgment.
The Holy Prophet of Islam (sallal laahu alaihi wasallam) said: Allah loosens the rope of the oppressor but when He tightens it, He gives no concession. Then Rasoolullah (sallal laahu alaihi wasallam) recited this verse: Even thus is the grasp of your Lord when He grasps the townships while they are doing wrong. Lo! His grasp is painful, very strong. (11: 102)
Sayyiduna Rasoolullah (sallal laahu alaihi wasallam) said: Don’t say that if people will good to us we shall do good to them and if they oppress us we shall oppress them. Do good if others do good to you and if they do wrong, don’t repay them in the same coins. (Tirmidi)
The Beloved Habeeb (sallal laahu alaihi wasallam) is reported to have said: Guard against the curse of an oppressed as he will demand his right from Allah and Allah will not deny him his right. (Bay’haqi)
At the last minute of his life, Sayyiduna Ali Ibne-Abi-Taalib (radi Allahu anhu) called upon his sons and gave them the advice: O my sons! Always be truthful, be merciful and helpful to the people. Try to slay the hand of the oppressor and help the oppressed.