The answer
The light that appears in the tomb is a symbol that the salvation process has taken place and that Christ was in Hades freeing the souls of the righteous from the place of darkness to the place of light.
H.G. Bishop Moussa
H.G. Bishop Moussa · Youth Concerns · 60
Faith Q&A › Youth Concerns › Theology, Doctrine, and Dogma
Why in Jerusalem does the light in the tomb appear on Saturday instead of Easter Sunday?
H.G. Bishop Moussa, Bishop of Youth, Youth Concerns (Questions & Answers). Compiled by Lisa Agaybi. Coptic Orthodox Patriarchate, Bishopric of Youth Bookstore.