What is the ruling concerning performing prayer before its prescribed time?
Chapter on what invalidates the prayer if omitted intentionally or forgetfully
Al-Mughni
Book of Prayer
Primary text
Every prayer for which a specific time is mandated is invalid if performed before that time begins. This rule is absolute for all prayers except the second prayer of a combined set (Jam'un).
Supporting text
The second prayer of a combined set, when two prayers are joined due to an excuse, may be performed during the time of the first prayer.