What does the unleavened bread picture about Israel after the exodus?
The unleavened bread pictured Israel as a separated people, set apart unto God after leaving Egypt. Because leaven symbolizes evil or sin, removing it showed they were no longer to be wrapped up in the paganism of their Egyptian masters but were to live separated from evil.
Les explains that leaven in Scripture always speaks of evil or sin. Yeast, or leaven, affects the whole lump, so evil, unless it is rooted out, will sooner or later affect the whole. In the exodus, Israel was to leave leaven out of their bread dough and bake unleavened cakes. The picture in type is that they were now to be a separated people, separated unto God, no longer wrapped up in the paganism of their Egyptian masters.
And they baked unleavened cakes of the dough which they brought forth out of Egypt, for it was not leavened; because they were thrust out of Egypt, and could not tarry, neither had they prepared for themselves any victual.