But God led the people around by the way of the wilderness toward the Red Sea. And the people of Israel went up out of the land of Egypt equipped for battle.
Exodus 13:18

Where did the Hebrews get weapons when they left Egypt? Surely Pharaoh didn't allow slaves to be armed. One tradition says "armed" in this verse should be translated "fifth" and only 1/5 of Israel survived the plagues. It could also be a metaphor of being prepared for spiritual warfare. I favor the literal interpretation. They were farmers, fishermen, and masons, so they had tools that could double as weapons. It's also possible that they had been secretly collecting weapons in Egypt in preparation for an armed uprising some day.