The soil around the bush was holy, while the soil on the sandals of Moses was common. The common cannot touch the holy without being transformed or destroyed (see “Clean, Unclean, and Holy” Theme Note). At the start of the exodus, God made it clear that he is completely different from his creation. This is important for a proper relationship between God and humans.
The word holy appears only a few times in the Bible before Exodus 3:5. It then becomes the main way to describe God in the Old Testament. In other Semitic languages, the same root word is rare. Semitic people were ancient groups from the Middle East and North Africa, known for their shared languages (such as Hebrew, Aramaic, or Arabic) and cultural traditions.
Holy does not describe a moral quality in these languages but simply what is “other than” human. Pagan gods were "holy" only in the sense of being “other.” They did everything humans do, both good and evil, but on a larger scale.
In the Bible, holiness first means being set apart. God alone is completely distinct from creation and worthy of being called holy in the fullest sense. His holiness includes moral perfection. He is perfectly consistent and moral in his character. Here, at the burning bush, God revealed his otherness. Later at Sinai, he revealed his moral character in his requirements for those who would be his covenant partners (see Exodus 19:6; 20:1–23:33; see also Leviticus 11:45; 1 Peter 1:13–16).