(40) باب اسْتِحْبَابِ التَّبْكِيرِ بِالصُّبْحِ فِي أَوَّلِ وَقْتِهَا وَهُوَ التَّغْلِيسُ وَبَيَانِ قَدْرِ الْقِرَاءَةِ فِيهَا
Sayyar b. Salama reported:
I heard Abu Barza saying that the Messenger of Allah (ﷺ) did not mind some delay in the 'Isha' prayer even up to midnight and he did not like sleeping before (observing it) and talking after it. Shu'ba said: I again met him (Sayyar b. Salama) for the second time and he said: Even up to the third (part) of the night.
Reference: Sahih Muslim 647 b
In-book reference: Book 5, Hadith 299
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1351