Quirks, Queries and Commentary—Exodus 3:18
It was at the burning bush where Moses, eighty years old, met God and received the instructions that would determine the rest of his life. He was to speak to the elders of Israel, tell them God’s intent to bring his people out of Egypt and then go to the king of Egypt and say these words that God gave him: “Let us take a three-day journey into the desert to offer sacrifices to the Lord our God.”
God had no intention of letting them return to Egypt after they had been gone for three days. It was a ruse, a lie, he told Moses to tell to accomplish his great purpose.