Sahih Muslim Book 45, Hadith 79
Allah, the Exalted and Glorious, grants respite to the oppessor. But when He lays Hand upon him, He does not then let him off. Re (the Holy Prophet) then recited this verse:" Such is the chastisement of thy Lord when He chastises the towns (inhabited by) wrongdoing persons. Surely, His punishment is painful, severe" (xi. 103).
“Rights will certainly be restored to those entitled to them on the Day of Resurrection, (to the point that) even the hornless sheep will lay claim upon the horned one.”
What is this, the proclamation of the days of jahiliya (ignorance)? They said: Allah's Messenger, there is nothing serious. The two young men fell into dispute and the one struck at the back of the other. Thereupon he (the Holy Prophet) said: Well, a person should help his brother whether he is an oppressor or an oppressed. If he is the oppressor he should prevent him from doing it, for that is his help; and if he is the oppressed he should be helped (against oppression).