7906. 'No yeast shall be found in your houses' means no falsity whatever shall come near good. This is clear from the meaning of 'yeast' as falsity, dealt with below; and from the meaning of 'house' as good, dealt with in Arcana Coelestia 3652, 3720, 4982, 7833-7835. The meaning of 'yeast' as falsity becomes clear from the places where yeast and anything made with yeast, and also where unleavened and anything made without yeast are mentioned, such as in Matthew,
Jesus said, Look out for and beware of the yeast of the Pharisees and Sadducees. Then the disciples understood that He had not said that they should beware of the yeast used in bread, but of the teaching of the Pharisees and Sadducees. Matthew 16:6, 11.
Here 'yeast' plainly stands for false teaching. Because 'yeast' meant falsity it was forbidden to sacrifice the blood of the sacrifice with anything made with yeast, Exodus 23:18; 34:25. For 'the blood of the sacrifice' meant holy truth, thus truth pure and free from all falsity, Arcana Coelestia 4735, 6978, 7317, 7326, 7846, 7850. It was also laid down that the minchah offered on the altar should not be baked with yeast in it, Leviticus 6:15-17, and that cakes and wafers also should be made without yeast, Leviticus 7:11-13.
Leviticus 6:14-17, 6:17; Matthew 16:12)
 To go further with what 'made with yeast' and 'not made with yeast' refer to, it should be recognized that the purification of truth from falsity cannot ever come about in a person without so called fermentation, that is, without the conflict of falsity with truth and of truth with falsity. But after the conflict has taken place and truth has triumphed, the falsity falls away like dregs and the truth emerges purified. It is like wine that becomes clear after fermentation as the dregs sink to the bottom. That fermentation or conflict takes place especially when a person's state undergoes a change, that is to say, when his actions begin to spring from the good of charity, and not as previously from the truth of faith. For a person's state is not yet made pure while his actions spring from the truth of faith, but they have been made pure when they spring from the good of charity, since they now spring from his will. Previously they sprang merely from his understanding.
 Spiritual conflicts or temptations are fermentations in the spiritual sense, for during them falsities wish to link themselves to truths, but the truths reject them, eventually sending them to the bottom so to speak and in that way becoming refined. This is the sense in which to understand what the Lord teaches about 'yeast' in Matthew,
The kingdom of heaven is like yeast, which a woman took and hid in three measures of flour, until the whole was fermented by it. Matthew 13:33.
'Flour' is truth from which good is derived. Also in Hosea,
They are all committing adultery, like an oven heated by a baker; the raiser 1
ceases from kneading the dough until it has fermented. Hosea 7:4.
Since such conflicts, meant by 'fermentations', take place with a person in the state before he attains newness of life, as has been stated, it was also laid down that the new minchah, the bread of the wave-offering, that was to be brought at the feast of first fruits, should be baked with yeast; and that was to be the first fruits to Jehovah, Leviticus 13:16, 17.
1. Whether the raiser means the stirrer of the fire or the raiser of the dough is not clear.
Exodus 12:19; Leviticus 6:14-17, 23:16-17)