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 Ils écouteront ta voix; et tu iras, toi et les anciens d'Israël, auprès du roi d'Egypte, et vous lui direz: L'Eternel, le Dieu des Hébreux, nous est apparu. Permets-nous de faire trois journées de marche dans le désert, pour offrir des sacrifices à l'Eternel, notre Dieu.