Sunan an-Nasa'i, Volume 1, Book 6, Hadith 533 (DarusSalam)

It was narrated that Ibn 'Abbas said: "The Prophet delayed 'Isha' one night until part of the night had passed. Then 'Umar, may Allah be pleased with him, got up and called out: 'The prayer, O Messenger of Allah! The women and children have gone to sleep.' Then the Messenger of Allah came out with water dripping from his head, saying: 'This is (the best) time (for 'Isha'), were it not that this would be too difficult for my Ummah.'"

أَخْبَرَنَا مُحَمَّدُ بْنُ مَنْصُورٍ الْمَكِّيُّ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ عَمْرٍو، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، وَعَنِ ابْنِ جُرَيْجٍ، عَنْ عَطَاءٍ، عَنِ ابْنِ عَبَّاسٍ، قَالَ أَخَّرَ النَّبِيُّ صلى الله عليه وسلم الْعِشَاءَ ذَاتَ لَيْلَةٍ حَتَّى ذَهَبَ مِنَ اللَّيْلِ فَقَامَ عُمَرُ - رضى الله عنه - فَنَادَى الصَّلاَةَ يَا رَسُولَ اللَّهِ رَقَدَ النِّسَاءُ وَالْوِلْدَانُ ‏.‏ فَخَرَجَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَالْمَاءُ يَقْطُرُ مِنْ رَأْسِهِ وَهُوَ يَقُولُ ‏ "‏ إِنَّهُ الْوَقْتُ لَوْلاَ أَنْ أَشُقَّ عَلَى أُمَّتِي ‏" ‏ ‏.‏

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also referenced under: Book 6, Hadith 537 (In-Book)