The fourth plague of Egypt was swarms of flies, which filled the homes and land of the Egyptians but left the Israelites in Goshen untouched. While most sources identify it as flies, some traditional interpretations debate whether the original Hebrew word meant a mixture of flies or wild beasts, with many commentators concluding it was wild animals. Regardless of the specific type of insect or animal, the plague was sent by God as a punishment after Pharaoh refused to let the Israelites go.