Oppression is of three types: dealing unjustly with Allaah (associating partners with Him), oppressing others and oppressing oneself.
Allaah says (interpretation of the meaning):
“The blame is only against those who oppress men with wrong-doing and insolently transgress beyond bounds through the land, defying right and justice: for such there will be a Penalty grievous.” (ash-Shura 42: 42)
Allah’s Messenger (peace and blessings be upon him) said that Allah the Exalted and Glorious said: “O My servants, I have taken it upon Myself to wrong no one; and have made oppression forbidden for you, so do not oppress one another.” (Muslim).
“Beware of oppression, for oppression will be a darkness on the Day of Resurrection.” (Muslim)
“He who has done a wrong affecting his brother’s honor or anything else, must ask his forgiveness for it today before the time when he will have neither a dinar nor a dirham. 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 in the same proportion of the one he wronged.” (Al-Bukhari)
…Abide by the truth even though your mind deserts you.