مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 597
Prayer
Observing Prayer Early in the Period - Section 1
وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانُوا يُصَلُّونَ الْعَتَمَةَ فِيمَا بَيْنَ أَنْ يغيب لاشفق إِلَى ثلث اللَّيْل الأول
‘A'isha said that they used to pray the night prayer at any time after the ending of the twilight until a third of the night had passed. (Bukhari and Muslim)
Mishkat al-Masabih, 597مُتَّفَقٌ عَلَيْهِ (الألباني)