זוהר שמות — דף קפב ע”א

When the Holy One Blessed Be He wished to unite with Israel in Egypt, the time was not right because the foreskin covered the light. The other side was busy with Iyov, and during that time the commandment was given to remove the foreskin from Israel. Eating leavened bread on Passover is like serving idolatry. Chametz is the evil inclination that enters a person little by little until the whole body is pervaded by it, like leaven in dough.