Is it permissible to delay the Isha, Shafa, and Witr prayers until half an hour or an hour before Fajr?

It is not permissible to delay the Isha prayer until after one-third or one-half of the night without a valid excuse, according to the Maliki and Hanbali schools. Whoever delays it without an excuse is considered sinful, though their prayer is still counted as performance (ada') and not a make-up (qada'). As for the Shafi'i and Hanafi schools, they hold that delaying it until this time is permissible, even if the preferred time is missed. It is preferable to delay the Shafa' and Witr prayers until the end of the night for those who are confident they will not miss them, because that is the time when the Lord, the Mighty and Exalted, descends to the lowest heaven, and the Prophet, peace and blessings be upon him, used to pray Witr until dawn (sahar).