At this point, Exodus moves from mostly narrative to mostly legislation (laws). While the Ten Commandments provide the broad outlines for behavior, more detailed laws are needed so that the Israelites can live together as a just society reflecting God’s own holy character. These laws are referred to as the Book of the Covenant. Sometimes, the justifications for specific laws aren’t clear (like the prohibition of chiseled stones). The prohibition of steps is probably connected to the risk of ritual impurity addressed in Chapter 19.