Is a Muslim considered sinful if he sleeps before the 'Isha prayer out of fatigue, knowing that he exerts effort to perform it and wakes up early for work?

The prayer must be performed on time, and it is not permissible to delay the Isha' prayer beyond its time. Sleeping before the Isha' prayer is disliked by most scholars, as the Messenger of Allah, peace and blessings be upon him, disliked it. The one who does so is not sinful unless he knows that he will not wake up to perform it on time. However, if he takes the necessary measures to wake up and only wakes up after the time has expired, then he is not sinful.