Aslam reported: Umar ibn al-Khattab, may Allah be pleased with him, appointed a client of his named Hunayy to tend the pasture and he said, “O Hunayy, lower your wing for the Muslims and beware the supplication of the oppressed, for the supplication of the oppressed is answered.”
Source: Ṣaḥīḥ al-Bukhārī 3059
Grade: Sahih (authentic) according to Al-Bukhari
عَنْ أَسْلَمَ أَنَّ عُمَرَ بْنَ الخَطَّابِ رَضِيَ اللَّهُ عَنْهُ اسْتَعْمَلَ مَوْلًى لَهُ يُدْعَى هُنَيًّا عَلَى الحِمَى فَقَالَ يَا هُنَيُّ ضْمُمْ جَنَاحَكَ عَنِ المُسْلِمِينَ وَاتَّقِ دَعْوَةَ المَظْلُومِ فَإِنَّ دَعْوَةَ المَظْلُومِ مُسْتَجَابَةٌ
3059 صحيح البخاري كتاب الجهاد والسير باب إذا أسلم قوم في دار الحرب ولهم مال وأرضون فهي لهم