Thabit narrates from Sayyiduna Anas (may Allah be pleased with him) concerning "the rising by night" [Surah al-Muzzammil: 6] that he said: "It is the time between Maghrib and Isha, and the Messenger of Allah (peace and blessings be upon him) used to pray between Maghrib and Isha."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4752