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’ (Exod 3:18).
As one commentator notes:
Verse 18 has given some readers pause. God seems to resort to deceptive measures when he instructs Moses and the elders to ask Pharaoh to allow them to go on a three-day journey into the open places to sacrifice to God, a kind of three day miniretreat. Is Moses to talk in such a way to lead Pharaoh to believe they will return to Egypt after a long weekend way? Is Greenberg (1969; 85) on target here? "Where wicked, superior force must be overcome for a just cause, an effective deception is as much a part of God's arsenal as miracle." Maybe twentieth-century Christians like Corrie Ten Boom and Brother Andrew would agree. There is an interesting phrase at the end of Ps 18:25-26 [26-27] (=2 Sam 22:26-27), part of David's thoughts about God: "To the faithful you show yourself faithful, to the blameless you show yourself blameless, to the pure you show yourself pure, but to the crooked you show yourself shrewd." V. Hamilton, Exodus (Baker 2011), 66-67.