Is it permissible to pray the 'Isha' prayer before sleeping, instead of at its prescribed time?

Allah Almighty says: "Indeed, prayer has been decreed upon the believers a timed ordinance" (Quran 4:103). This means it is fixed at a specific time, and prayer is not valid before its time, by the consensus of Muslims. So, whoever prays intentionally before the time, their prayer is invalid and they are sinful. If they did so unintentionally, believing the time had entered, then they are not sinful, but their prayer is considered a voluntary prayer (nafl), and they must repeat it, because time is one of the conditions for the validity of prayer.