And there are two views on this: the first is a third of the night, and the second is half of the night. So whoever adopted the first view argued from the following.
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "Jibril (peace be upon him) led me in prayer twice at the House (of Allah)," and he mentioned the hadith. In it is: "He led me in the Isha prayer in the first third of the night," meaning the second time.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1749