Is it true that an oppressed persons prayers are answered quickly by Allah and we should avoid oppressing people. I want a detailed answer as much as possible for this question.
In Mustadrak it is mentioned Oh Muslims take refuge from prayer of oppressed as it goes to sky like spark in fire. It is also clear from Hadees prayers of ill people are very very close to Allah.
But you should be more worried when you are doing wrong with an oppressed person. If you haven't done anything wrong and oppression is done by someone else then it is not your fault. And also keep in mind every oppressed looking person might not be oppressed.