Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.086.

Section : The Time of the Night Prayer (‘Isha).

This prayer begins when the red twilight disappears and continues up to half of the night. Reported ‘Aishah, “They used to pray the night prayer between the disappearance of the twilight and the final third of the night’s beginning.” (Related by al-Bukhari.) Abu Hurairah reported that the Messenger of Allah, upon whom be peace, said, “If it were not to be a hardship upon my nation, I would order them to delay the night prayer until a third or a half of the night had passed.” (Related by Ahmad, Ibn Majah and at-Tirmizhi, who said it is sahih.) Reported Abu Sa’eed, “Once, we waited for the Messenger of Allah to lead the night prayer until half the night had passed, at which time he came and prayed with us. He said, ‘Stay in your places of sitting while the people have gone to their places of lying down (for sleep), for you are in prayer as long as you are waiting for the prayer. If it were not for the weakness of the weak, the illness of the ill and the need of those who have needs, I would have delayed the time of this prayer to a half of the night.”

As to the authenticity of this report, it is recorded by Ahmad, Abu Dawud, Ibn Majah, an-Nasa’i and Ibn Khuzaimah. Its chain is sahih). The hadith describes the best time to pray. As for the allowable time and the time due to need, it lasts until dawn. Abu Qatadah reported that the Messenger of Allah, upon whom be peace, said, “There is no negligence in sleeping, but the negligence lies in not praying a prayer until the time of the next prayer has come.” (Related by Muslim.) This hadith shows that the time of every prayer continues until the beginning of the time for the next prayer, except for the morning prayer, as all scholars agree that its time lasts only until sunrise.