God reveals to his prophets what he will do (see Amos 3:7). He did so with Abraham (the first man in the Bible who is called a prophet, Genesis 20:7). God’s plan was to destroy Sodom and Gomorrah, but before doing it, he asked himself, Shall I hide from Abraham what I am about to do?
(Genesis 18:17). God gave Abraham the opportunity to plead for Sodom. In Exodus 32:1–35, during the worship of the golden calf, God revealed to Moses that he was going to destroy Israel; but Moses pleaded for the people—with result.
Here in Exodus 3, God reveals the elders will accept his message and the Pharaoh will refuse to listen. It is an encouragement to Moses when it happens (in Exodus 4:30 and Exodus 5:2). God is in control. He fulfills his promises.
18 And they will listen to your voice, and you and the elders of Israel shall go to the king of Egypt and say to him, ‘The LORD, the God of the Hebrews, has met with us; and now, please let us go a three days’ journey into the wilderness, that we may sacrifice to the LORD our God.’