Oppression is from the most disgusting, despicable of major sins, it’s evil consequences Allāh (The Glorified) has informed us of in His Tremendous Book:
وَمَن يَظْلِم مِّنكُمْ نُذِقْهُ عَذَابًا كَبِيرًا
And whoever among you does wrong, We shall make him taste a great torment. (Al-Furqān: 19)
And Allāh says:
وَالظَّالِمُونَ مَا لَهُم مِّن وَلِيٍّ وَلَا نَصِيرٍ
And the Dhālimun (polytheists and wrong-doers, etc.) will have neither a Wali (protector) nor a helper. (Ash-Shūra: 8)
Hence, oppression is a great evil and it has evil consequences, the Messenger (sallāhu alayhi wa salam) said:
“Fear oppression for indeed oppression is darkness on the day of resurrection.” (Muslim)
Furthermore, Allāh has said in a Hadīth Qudsī (which is narrated by the Prophet (sallāhu alayhi wa salam)):
“Oh my servant! Indeed I have forbidden oppression upon myself and between you, so do not oppress.” (Muslim)
Therefore, it is obligatory to be cautious of perpetrating oppression to any of the people, whether it be your family, your wife, your brothers, your children, your mother, your father, your neighbours and other than them.
Likewise, do not oppress your employees, give them their wages in full, every month (for e.g.) give him or her their wages.
Give everyone who has a right upon you; your children, your wife and other than them; their rights.
The intent in being cautious regarding oppression of the people is because indeed Allāh has made sacred the blood, honour and wealth of the Muslims.
So, the Muslim takes himself to account and fears his Lord, so do not oppress anyone, not their honour or their wealth, regardless of whether they are close to you or not.
Paraphrased from Shaykh ‘Abdul Azīz ibn Bāz: