According to the story, when Hebrews left Egypt, they had to escape so quickly that they did not have time for the bread to rise, so they made unleavened bread called matza (matzo). But there is another reason why the Exodus and unleavened bread are connected. Passover happens each year on a different day in March or April, according to the lunisolar calendar. In Israel, this is when people began to harvest barley. They made bread without leaven from the new barley, because the leaven would have to come from last year’s barley. Later, Israelite priests combined the two festivals into one.