What was the reasoning behind no yeast?
>>What was the reasoning behind no yeast?<<
Fear of a yeast infection?
The Bible speaks of leaven as something that "puffs up" things, and there are things in our lives and hearts that can "puff us up" too, including vanity, greed, wicked thoughts, and more. The preparations for this special time calls the Jews to meditate on what may be puffing up their lives, while they physically remove "puffing agents" and puffy baked goods from their cupboards.
Fermentation (leavening) also talks about false doctrine. The Lord said to His disciples "Beware of the leaven (false doctrine) of the Pharisees" (Matthew 16:6; Mark 8:15).
Finally, yeast/leaven represents decay, i.e. the grave.
One reason is to teach people about how easy it is to sin. Yeast is used to represent sin and you have to remove the yeast out of your house and life for a week to physically represent removing sin from your whole life. A little yeast affects the whole loaf as in a little sin can corrupt the whole individual.
I imagine it is harder to follow unleavened bread today than it was in old Israel. We are surrounded by rolls, muffins, pancakes, hamburgers... It might be like life in general. We have a lot more temptations to avoid today (bad movies, filth on the internet, etc).
Another big reason has to to with remembering the quick departure from Egypt and what God did to bring his people out of slavery.
I guess there are other things, too. I wouldn’t be surprised if it also had a hygiene reason. God set down a lot of rules that improved the lives of his people. Not all were understood. Modern science has shone several to have great merit (not eating pork or shrimp, handling of unclean clothing and people with disease)
The bread of haste.