Matthew Henry Commentary Exodus 13:17-20

"And it came to pass, when Pharaoh had let the people go, that God led them not by the way of the land of the Philistines, although that was near; for God said, Lest peradventure the people repent when they see war, and they return to Egypt: but God led the people about, by the way of the wilderness by the Red Sea: and the children of Israel went up armed out of the land of Egypt. And Moses took the bones of Joseph with him: for he had straitly sworn the children of Israel, saying, God will surely visit you; and ye shall carry up my bones away hence with you. And they took their journey from Succoth, and encamped in Etham, in the edge of the wilderness." — Exodus 13:17-20 (ASV)

There were two ways from Egypt to Canaan. One was only a few days' journey; the other was much farther around, through the wilderness, and that was the way in which God chose to lead his people Israel. The Egyptians were to be drowned in the Red Sea; the Israelites were to be humbled and tested in the wilderness.

God's way is the right way, though it seems roundabout. If we think he does not lead his people the nearest way, yet we can be sure he leads them the best way, and it will become clear when we come to our journey's end. The Philistines were powerful enemies; it was necessary that the Israelites should be prepared for the wars of Canaan by passing through the difficulties of the wilderness.

Thus God proportions his people's trials to their strength, 1 Corinthians 10:13. They went up in good order: some say in ranks of five; others, in five companies. This detail seems to relate more to their faith and hope that God would bring them to Canaan, in expectation of which they carried these bones with them through the desert.