What does Exodus 3:18 mean?
This is part of God's message to the "elders of Israel," to be delivered by Moses when he returns to Egypt. God has already stated His intention to free Israel from their oppression, and to give them control of a prosperous homeland.God also promised Moses the Israelite elders would "listen to your voice." Moses was initially concerned that the Hebrews still living in Egypt would have no desire to listen to him (Exodus 2:14; Exodus 3:13). And yet, God's prediction here will be confirmed; Exodus 4:31 says "the people believed" the message of Moses and his brother Aaron.
The next step in God's plan is for Moses and the elders of Israel to confront the king of Egypt—the Pharaoh—and request a three-day journey into the wilderness to make sacrifices to the Lord. Some have asked why God would instruct Israel to make this request, since the ultimate plan was to free Israel from Egypt entirely. In part, this request is meant to show the obstinacy of Egypt's rulers—they won't even approve such a minor detour, let alone complete freedom.
The completion of this order takes place in Exodus 5:3. As expected, Pharaoh rejects the request, instead forcing the Jews to make bricks without straw, a move that greatly increases their workload. God will follow this event with the plagues predicted later in this chapter (Exodus 3:20; 7—12). This request for a three-day journey is also repeated in Exodus 8:27. Interestingly, the plague of darkness would last three days, with no one working during this time (Exodus 10:22–23). Once again, Egypt's attempts to thwart God will result in the exact consequences they seek to avoid.