There are three whose supplications are not turned back: A just ruler, and a fasting person until he breaks his fast. And, the supplication of one who has been wronged is raised by Allah up to the clouds on the Day of Resurrection, and the gates of heaven are opened for it, and Allah says, ‘By My Might I will help you (against the wrongdoer) even if it is after a while.’”  

عَنْ سَعْدٍ أَبِي مُجَاهِدٍ الطَّائِيِّ وَكَانَ ثِقَةً عَنْ أَبِي مُدِلَّةَ وَكَانَ ثِقَةً عَنْ أَبِي هُرَيْرَةَ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ ثَلاَثَةٌ لاَ تُرَدُّ دَعْوَتُهُمُ الإِمَامُ الْعَادِلُ وَالصَّائِمُ حَتَّى يُفْطِرَ وَدَعْوَةُ الْمَظْلُومِ يَرْفَعُهَا اللَّهُ دُونَ الْغَمَامِ يَوْمَ الْقِيَامَةِ وَتُفْتَحُ لَهَا أَبْوَابُ السَّمَاءِ وَيَقُولُ بِعِزَّتِي لأَنْصُرَنَّكِ وَلَوْ بَعْدَ حِينٍ  

“When the fasting person breaks his fast, his supplication is not turned back.” (One of the narrators) Ibn Abi Mulaikah said: "When he broke his fast, I heard 'Abdullah bin 'Amr say: 'O Allah! I ask You by Your mercy, which encompasses all things, to forgive me.'"  

قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ لِلصَّائِمِ عِنْدَ فِطْرِهِ لَدَعْوَةً مَا تُرَدُّ قَالَ ابْنُ أَبِي مُلَيْكَةَ سَمِعْتُ عَبْدَ اللَّهِ بْنَ عَمْرٍو يَقُولُ إِذَا أَفْطَرَ اللَّهُمَّ إِنِّي أَسْأَلُكَ بِرَحْمَتِكَ الَّتِي وَسِعَتْ كُلَّ شَىْءٍ أَنْ تَغْفِرَ لِي