What is the ruling on the prayer of someone who intended to pray 'Isha at nine o'clock, then slept and woke up at one o'clock and prayed?

If you sleep after the time for the 'Isha prayer has begun, and you know that you will wake up to perform it within its preferred time, then there is no sin upon you. However, if you know that sleep will consume the preferred prayer time, such that you will not wake up until after one-third or half of the night has passed, then you are sinful and must repent. Some scholars, such as the Shafi'is, hold the view that the 'Isha prayer does not have a time of necessity, and in this case, you are not sinful for delaying it.