What scripture tells us why Jesus gave us unleavened bread for Passover day?

Answer 1

the bread was unleavened because fleeing Egypt they did not have enough time to let the dough rise before baking it.

That's why its called UNleavened bread

As they were expelled from Egypt they put their bread in sacks and it baked on their backs as they walked across the desert.

Answer 2

"Unleavened bread" (matstsohth) is bread WITHOUT yeast.

Moses was instructed by God to tell the Israelites to eat NOTHING leavened when they began the exodus from Egypt(Exodus 13:3)(Exodus 34:25)(Deuteronomy 16:3) and this continued through all Passover celebrations(Numbers 9:11). Unleavened bread was a reminder to the Jews of their haste at leaving Egypt(no time to let the bread rise), as God rescued them from Egyptian bondage.

It also PRE-figured the coming of the Messiah who would rescue man from their sins, permanently. Yeast often symbolized 'imperfection'...a bad influence spreading...like a little "leaven fermenting the whole lump" (Galatians 5:9).

UNleavened bread symbolized purity (with nothing added)so was appropriate for representing Jesus' sinless fleshly body (Hebrews 7:26; 9:14; 1Peter 2:22, 24) that was given in our behalf(Luke 22:19, 20). Christ was the ultimate Passover sacrifice(1 Corinthians 5:6-8) (John 1:29).