What does Exodus 12:20 mean?

This continues (Exodus 12:19) to repeat instructions given regarding the Feast of Unleavened Bread (Exodus 12:15). All leaven, or yeast, was to be removed from all homes. This meant eating un-risen bread (Exodus 12:8), which provided Israel with food to carry when they were suddenly freed from slavery (Exodus 12:33, 39). Leaven also became a metaphor for sin (1 Corinthians 5:6–8). Israel is to commemorate these events for a week-long period each year, beginning immediately after celebrating Passover (Exodus 12:18).

Violating these commands came with serious consequences. Disobedience meant being "cut off" from Israel: rejected and ostracized from the community and thus all the covenant promises of God's people (Genesis 17:14).