CLAIM: God cannot lie (Heb. 6:18; Titus 1:2), and yet, this statement seems to be deceiving. God wasn’t planning on taking them for “three days,” as this passage claims. Instead, he was planning on taking them permanently from the Egyptians.
RESPONSE: God may have given an easier request at first to demonstrate how unreasonable the Pharaoh was in relieving the Hebrew slaves. God, in his foreknowledge, knew that Pharaoh wouldn’t release the Jews no matter what (see v.19). This may have revealed to the people just how cruel Pharaoh was. On the other hand, Douglas Stuart argues that people in the ancient Near East typically didn’t ask for their requests directly.Instead, they usually asked for things indirectly. A modern equivalent might be, “Would you give me the remote control?” or “Can I have the keys to the car tonight?” These loaded questions are indirect ways of controlling the TV channel or taking the car out for the night. Stuart argues that this expression was indicative of a long trip (“We’re going to leave for as long as we want.”).
 Stuart, Douglas K. The New American Bible Commentary: Exodus. Vol. 2. Nashville, TN: B & H Group, 2006. 124-125.