What is the ruling on the Imam leading the 'Isha prayer before its prescribed time, under the pretext that people need to go to their work, knowing that prayer "was enjoined on the believers at fixed times"?

The time for the Isha prayer begins when the red twilight disappears. If the Imam prays after the time has begun, his prayer is valid. However, he should consider the condition of the congregation and wait for their presence. There is no difference in the Isha prayer time between summer nights and others; the time begins with the disappearance of the red twilight. Before that, neither the prayer nor the Adhan (definition) is permissible, whether the night is long or short.