What did the seven days of unleavened bread after Passover picture for Israel?
The seven days of unleavened bread pictured Israel as a nation whose sins had been atoned for or cleansed. The unleavened bread symbolized that cleansing, while leaven pictured sin; after Passover, Israel was to live as a people cleansed from sin.
Les explains that this went all the way back to the Passover in Egypt, and the very next day after Passover was the seven days of unleavened bread. Israel was now to be pictured as a nation whose sins had been atoned for or cleansed, and they were to picture that with the unleavened bread. Paul brings that same analogy into our teaching today: we have to look at sin in our individual lives and in the life of the church, just like the leaven in the bread of Egypt. To be unleavened means we have been forgiven and cleansed, and so far as God is concerned, without sin. But if a little leaven is left in our life, it will expand and consume us again. Even as Christ our Passover is sacrificed for us.