حَدَّثَنَا إِسْمَاعِيلُ قَالَ‏:‏ حَدَّثَنِي مَالِكٌ، عَنْ أَبِي حَازِمٍ، عَنْ سَهْلِ بْنِ سَعْدٍ قَالَ‏:‏ سَاعَتَانِ تُفْتَحُ لَهُمَا أَبْوَابُ السَّمَاءِ، وَقَلَّ دَاعٍ تُرَدُّ عَلَيْهِ دَعْوَتُهُ‏:‏ حِينَ يَحْضُرُ النِّدَاءُ، وَالصَّفُّ فِي سَبِيلِ اللهِ‏.‏
Translation
Sahl ibn Sa'd said, "There are two hours in which the gates ofheaven are opened. At those times very rarely is the supplication of someonewho makes supplication rejected

when the call to prayer has been givenand when in battle ranks in the Cause of Allah."