Mishkat al-Masabih 2249
Abu Huraira reported God’s messenger as saying, “There are three whose supplication is not rejected:
one who has just ended a fast, a just imam , and one who has been wronged whose supplication is raised by God above the clouds and for which the gates of heaven are opened. The Lord says, ‘I swear by my might that I will certainly help you, though it be after some time’.” 

Tirmidhi transmitted it.
وَعَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: 
" ثَلَاثَةٌ لَا تُرَدُّ دَعْوَتُهُمْ: الصَّائِمُ حِينَ يُفْطِرُ وَالْإِمَامُ الْعَادِلُ وَدَعْوَةُ الْمَظْلُومِ يَرْفَعُهَا اللَّهُ فَوْقَ الْغَمَامِ وَتُفْتَحُ لَهَا أَبْوَابُ السَّمَاءِ وَيَقُولُ الرَّبُّ: وَعِزَّتِي لَأَنْصُرَنَّكِ وَلَوْ بعد حِين ". رَوَاهُ التِّرْمِذِيّ