Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "The supplication of the oppressed is answered, even if he is a sinner, for his being a sinner will count against himself."
(Allamah al-Haythami says:) I say: Imam Abu Dawud has recorded from this Companion a narration about the supplication of the oppressed, which is other than this narration.
Imam Ahmad recorded this narration, Imam al-Bazzar recorded something similar, and its chain is hasan (good).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدعية / 17227
Hadith Gradingمحدثین:إسنادہ حسن
Hadith Takhrij«اخرجه الطبراني فى المعجم الاوسط (1204) اخرجه احمد فى المسند (367/2) ، أخرجه مسند أحمد برقم: 8577»