Bulugh al-Maram 67
Narrated Anas (rad):
The Companions of Allah’s Messenger (ﷺ) in his lifetime used to wait for the ‘Isha (night) prayer, so much so that their heads were lowered down  (by dozing). They would then pray without performing ablution. [Reported by Abu Da’ud and Ad-Daraqutni graded it Sahih (sound). Its origin is in Muslim].
عَنْ أَنَسِ بْنِ مَالِكٍ ‏- رضى الله عنه ‏- قَالَ: { كَانَ أَصْحَابُ رَسُولِ اَللَّهِ ‏- صلى الله عليه وسلم ‏-‏-عَلَى عَهْدِهِ‏- يَنْتَظِرُونَ اَلْعِشَاءَ حَتَّى تَخْفِقَ رُؤُوسُهُمْ, ثُمَّ يُصَلُّونَ وَلَا يَتَوَضَّئُونَ }  أَخْرَجَهُ أَبُو دَاوُدَ, وَصَحَّحَهُ اَلدَّارَقُطْنِيّ ُ  1‏ .‏‏1 ‏- صحيح .‏ رواه أبو داود (200)‏، والدارقطني (1/131/3)‏ وقال الدار قطني: صحيح .‏