Is it permissible to pray Fajr before its prescribed time, or to combine prayers upon returning home, for one who leaves for work before the prayer time?

A Muslim is not permitted to pray Fajr before its prescribed time, because the validity of prayer is conditioned upon the entry of its time. It is also not permissible to combine all prayers upon returning home, for each prayer has a specific time when it must be performed, and it is not permissible to perform it before or after its time, except for those who are allowed to combine prayers that are permissible to combine, which are Dhuhr with Asr and Maghrib with Isha. Every prayer must be performed at its appointed time.