Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated that when the Prophet Muhammad (peace and blessings be upon him) sent Sayyiduna Mu'adh (may Allah be pleased with him) to Yemen (as a governor), he instructed him: "Beware of the supplication of the oppressed, for there is no barrier between it and Allah, the Exalted."
Hadith Referenceاللؤلؤ والمرجان / كتاب الايمان / 12
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 46 كتاب المظالم: 9 باب الاتقاء والحذر من دعوة المظلوم»