بُلُوغُ الْمَرَامِ
Bulugh al-Maram 158
The Book of Prayer
وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا قَالَتْ: { أَعْتَمَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -ذَاتَ لَيْلَةٍ بِالْعَشَاءِ, حَتَّى ذَهَبَ عَامَّةُ اَللَّيْلِ, ثُمَّ خَرَجَ, فَصَلَّى, وَقَالَ: إِنَّهُ لَوَقْتُهَا لَوْلَا أَنْ أَشُقَّ عَلَى أُمَّتِي } رَوَاهُ مُسْلِمٌ [1] .
Narrated 'Aishah (RA): The Prophet (ﷺ) delayed (the 'Isha' prayer) one night till a great part of the night passed, then he went out and offered the prayer, and said, "This is the proper time for it; were it not that I would impose a burden on my followers." [Reported by Muslim].
Sunnah.com reference: Book 2, Hadith 8