For something to be "unleavened" means that it's been made without yeast. Since yeast is what makes bread rise and take on its airy texture, unleavened bread is relatively flat, dense and hard. The idea that unleavened bread is holy appears in both the Old and New Testaments and is still part of both Jewish and Christian traditions.

In the Word, bread represents the desire for what is good -- which gives us spiritual energy, just as bread gives us natural energy. Yeast, meanwhile, represents falsity -- so that bread made without yeast is a pure desire for good, free of falsity. This also makes sense because air represents our capacity to understand what's true -- which is the same capacity we use to embrace ideas that are false. Yeast causes bread to rise by producing gases as it ferments, thus adding "bad" air to the bread.

1679. 'And they smote all the territory of the Amalekites' means kinds of falsities. This is clear from the representation and meaning of the 'Amalekite' nation, for all the nations that were in the land of Canaan represented kinds of falsities and evils, as will be clear, in the Lord's Divine mercy, from what follows. 'The Amalekites' means falsities, 'the Amorites in Hazezon-tamar' evils deriving from falsities. That 'the Amalekites' means falsities which assail truths becomes clear from what is mentioned regarding the Amalekites in Exodus 17:13-end; Numbers 13:29; 24:20; Deuteronomy 25:17-19; Judges 5:14; 1 Samuel 15:1-end; 1 Samuel 27:8; Psalms 83:7-8.

[2] The Rephaim, Zuzim, Emim, and Horites, referred to in verses 5-6, mean false persuasions that have their origins in desires for evil, that is, in evils, whereas here 'the Amalekites and the Amorites in Hazezon-tamar' means falsities from which evils derive. Falsity deriving from evil is one thing, falsity and evil deriving from that falsity another. Falsities spring either from evil desires which belong to the will or from accepted ideas which belong to the understanding. Falsities that spring from evil desires belonging to the will are foul and do not easily allow themselves to be rooted out, for they cling to a person's life itself. A person's life itself is that which desires, that is, which loves. As long as he is making that life firm within himself, that is, confirming that desire or love, all things of a confirmatory nature are false and are implanted in his life. Such were the people before the Flood.

[3] Falsities however which spring from accepted ideas belonging to the understanding cannot be rooted in the same way in the will part of man's mind. Like false or heretical doctrines, these have their origin outside of the will, coming instead from the absorption of such matters in early childhood, and after that from the confirmation of them in adult years. Yet because they are false they inevitably produce evils of life. For example, when anyone believes that he merits salvation through works and confirms himself in that belief, a sense of merit, of his own righteousness, and of assurance [of salvation] are the evils that result from it. On the other hand, when anyone believes that a truly devout life is not possible unless merit is attached to works, the evil which results from that belief is that he destroys all such devoutness in himself and gives himself up to evil desires and pleasures. It is the same with many other examples that could be taken. Such are the falsities and derivative evils dealt with in this verse.