God’s holiness is a great theme in the Sinai passages. We see this in the way that the Law tells his people how to live in his holy presence and in the conditions that are set. There is a delineation between who can approach YHWH and who cannot. Some of the people can come so far with Moses but no further. There are boundaries set that are not to be crossed. This theme will be picked up by the structure of the Tabernacle/Temple and the roles of the priests. It however is not a new theme. Genesis 1-3 points to God as the one who brings order through boundaries such as the distinctions between day and night, sea and sky, and land and sea. God sets boundaries in Eden, around the garden for Adam to guard and within the garden through the limit on which trees he could eat from. The sin of the sons of God in Genesis 6 also seems to be a case of boundary crossing. God will set new boundaries in Genesis 9 protecting the life blood of animals and humankind.
Holiness therefore seems to be both a challenge and a blessing. The Israelites fear God ands we know from Deuteronomy 1 that they themselves ask Moses to mediate. God sets boundaries because there is danger in approaching him. However, God’s holiness is a blessing. The people need both the order and purity it brings as well as the power, as God sends his “terror” ahead of him. It’s his holiness that drives out the enemies. His holiness is necessary but mediated through Moses and through angels.