The symbol of leaven had a dual function in the tradition of the Passover:
- Leaven was excluded from bread so that it was quicker to bake, carry and eat - the escaping population. In Ex 12:11, the Israelites were to eat it dress and while standing and in haste - ready to escape quickly. See also V33, 34, 39, etc.
Note the comments of the Cambridge commentary:
[Ex 12:8] unleavened cakes not ‘bread,’ for the Heb. word is plural. They were a kind of biscuit, which could be baked rapidly, as for an
unexpected visitor (Genesis 19:3, Jdg 6:19-21, 1 Samuel 28:24), or
when there was no time to use leaven (below, v. 39); and they are
still the ordinary food of the Bedawin.
Benson is similar:
[Ex 12:8] Unleavened bread — Partly to remind them of their hardships in Egypt,
unleavened bread being more heavy and unsavoury; and partly to
commemorate their hasty deliverance, which did not allow them time to
leaven it, Exodus 12:39;
- Leaven represented sin and the purging of leaven from the house represented the holiness of the people (Ex 19:5, 6).
- 1 Cor 5:8 - Therefore let us keep the feast, not with the old bread, leavened with malice and wickedness, but with the unleavened bread of sincerity and of truth.
- 1 Cor 5:7 - Get rid of the old leaven, that you may be a new unleavened batch, as you really are. For Christ, our Passover lamb, has been sacrificed.
- 1 Cor 5:6 - Your boasting is not good. Do you not know that a little leaven works through the whole batch of dough? See also Gal 5:9.
- Luke 12:1 - In the meantime, a crowd of many thousands had gathered, so that they were trampling one another. Jesus began to speak first to His disciples: “Beware of the leaven of the Pharisees, which is hypocrisy.
- Matt 16:6 - “Watch out!” Jesus told them. “Beware of the leaven [sinful teachings and practices] of the Pharisees and Sadducees.” See also V11
- Matt 16:12 - Then they understood that He was not telling them to beware of the leaven used in bread, but of the teaching of the Pharisees and Sadducees.
Note the comments of Ellicott:
[Ex 12:8] Unleavened bread . . . bitter herbs.—As partaking of the lamb typified feeding on Christ, so the putting away of leaven and eating
unleavened bread signified the putting away of all defilement and
corruption ere we approach Christ to feed on Him (1Corinthians 5:8).
As for the bitter herbs, they probably represented “self-denial” or
“repentance”—fitting concomitants of the holy feast, where the Lamb of
God is our food. At any rate, they were a protest against that
animalism which turns a sacred banquet into a means of gratifying the
appetite (1Corinthians 11:20-22).
Matthew Poole summarizes this in his comments on Ex 12:8 -
Unleavened bread; partly, as a monument of their speedy departure out of Egypt, which gave them not time to leaven their bread, Exodus
12:34, which is the reason alleged for it, Deu 16:3; partly, to teach
us how men should be qualified that come to the sacrament, they should
be purged from error, and pride, and malice, and hypocrisy, which are
called and compared to leaven, Matthew 16:6,11 Lu 12:1 1 Corinthians
5:8; and partly, to signify the singular purity of Christ from all
kind of spiritual leaven.
