Question:

Can you explain fully why it appears that God asked Moses to ask Pharaoh to let His people go a 3-day journey into the wilderness to hold a sacrifice to the Lord? Exodus chapters 3-5 deals with this. The Lord answers the question by saying He is sure that Pharaoh will not let them go. And later God says that He will harden his heart, and of course the New Testament speaks to that. But it seems almost deceptive to ask for only 3 days, as if they would return to Egypt after that. Obviously the plan of God was to redeem His people and bring them into the promised land. So why the use of the 3-day ploy?

Answer:

Grace and peace to you from God our Father and the Lord Jesus Christ.

You asked: "Why did God tell Moses to ask Pharaoh for 3 days off from work, when God intended to liberate the Israelites from Pharaoh's dominion altogether?"

Here's an answer:

Part of the answer is this: Do not be misled; there is no deceit here.

Part of the answer is that we have here a public demonstration of Pharaoh's arrogance and of his obstinate, foolish claim to unlimited power over all the Israelites, who were God's inheritance. Pharaoh is a boaster; God is not a boaster. He states what He is going to do and does it:

Isaiah 46:9-10:
⁹Remember the former things of old: for I am God, and there is none else; I am God, and there is none like me,
¹⁰Declaring the end from the beginning, and from ancient times the things that are not yet done, saying, My counsel shall stand, and I will do all my pleasure."

Note also Genesis 15:13-14. Here God tells Abraham that his descendants will be in servitude and then they will come out with riches and be given the land of Palestine.

Pharaoh did not know God's plan, but that is not the end of the story. Pharaoh's sins and civil corruption led him to say to Moses, "Who is Jehovah that I should listen to him?"

God came to Pharaoh by the mouth of Moses, leader of the Israelites, Pharaoh's Hebrew slaves. The Hebrew slaves were led by God, via Moses, to ask permission of their ruler to go three days journey and worship Jehovah-God. God directed the asking of a modest request. The Israelite request in the Name of their God also let Pharaoh know that their worship was different than the worship of Egyptians and other pagans. The Israelites were not allowed to act in a manner that encouraged anarchy, such as by just secretly marching off. Nor were they allowed to worship as fallen man willed. They had to go to meet with God at the appointed place and worship as God prescribed.

Pharaoh refused all the requests and resisted all claims of God upon the Hebrew slaves. Was Pharaoh right? No! Was he innocent and being a just and wise ruler? No!

It is a mistake to suppose God intended to deceive Pharaoh. God forbids the practice of deception and deceit. It ought rather to be seen that God entered into the desperate case of the Israelites. God did not enter into an earthly controversy over traditions, but into a religious issue with Pharaoh. God tells Moses to call Jehovah the God of the Hebrews, in Pharaoh's presence, because His grace and the true, restored knowledge of God as Creator, Provider, Judge, Savior, and Covenant-Keeping Author of the Covenant of Grace are peculiar to the Hebrews. All the rights of kings must give way before the religious rights of their subject people to worship God according to God's prescriptions.

Pharaoh denied any need on his part to limit his rule when God has summoned His people to worship. By the mouth of Moses, Pharaoh was told that the God of the Hebrews' name is "My Will will be done" or as it is often translated, "I will be what I will be." Jehovah sent Moses with a message that challenged Pharaoh's will in an orderly, non-anarchical manner.

Pharaoh, step by step, hardened his heart and dealt deceitfully with Moses, Israel, and God until God used Pharaoh's greed to drown him and all his army between the walls of the Red Sea. God shed no saving grace upon Pharaoh, but rather hardened his heart. It was never an issue of 3 days versus an Exodus. From beginning to end it was an issue of whose will would be done—Pharaoh's or Jehovah's.

Below is a quotation from the esteemed John Calvin (Harmony of the Law in Exodus, Numbers, Deuteronomy and Leviticus, Vol 1, pp. 78-79) on Exodus 3:18, which also may be helpful:

18. "And they shall hearken to thy voice." The literal translation is, "They shall hearken to thy voice," which many take to be a promise from God that they should be obedient; but the sense given in the Latin, "after they shall have heard thy voice," seems more consonant, that first of all He should command them by the mouth of Moses, and that then they should accompany him in bearing the message to Pharaoh. For, before so difficult an undertaking was enjoined to them, it was desirable that the authority of God should be propounded to them, so that they might go about it with unwavering hearts.

The sum of the message is, that they should seek permission from Pharaoh to go and sacrifice; but lest they might be thought to do so from mere unfounded impulse, they are desired to premise that God had met with them and had given them the command. For the word which expresses his meeting with them, means that he presented himself voluntarily. They had indeed cried out before, and often appealed to the faithfulness and mercy of God; yet still this was a voluntary meeting with them, when, contrary to the hope of them all, he avowed that he would be their deliverer, for, as we have already said, they cried out more from the urgency of their affliction than from confidence in prayer.

A pretext is suggested to them, by which suspicion and anger may be turned away from themselves; for a free permission to depart altogether, by which grievous loss would have arisen to the tyrant, never would have been accorded. Besides, by refusing so equitable a demand, he despoiled himself of his royal right and power, since he thus withheld His due honor from the King of kings; for although the Israelites were under his dominion, yet did not his rule extend so far as to defraud God of his rightful worship. It was expedient, too, that the people should depart without the king's permission only for very good reasons, lest hereafter license of rebellion should be given to other subjects.

Pharaoh indeed suspected differently, that the sacrifice was a mere false pretense; but since this mistrust proceeded from his tyranny, his ingratitude was sufficiently proclaimed by it, because through his own evil conscience he forbade that God should be served. Whatever, again, might be his feelings, still the miracles by which the command was followed must needs have taught him that their mission proceeded from God. If the Israelites had merely spoken, and no confirmation of their words had been given, he might perhaps have naturally guarded himself against deception; but when God openly showed that he was the originator of this departure, and that he commanded the sacrifice beyond the bounds of Egypt, all grounds of excuse are taken away; and thus the departure of the people is placed out of the reach of calumny.

If any object that it is alien from the nature of God to countenance any craft or pretense, the reply is easy,—that he was bound by no necessity to lay open his whole counsel to the tyrant. They mistake who suppose that there is a kind of falsehood implied in these words; for God had no desire that his people should use any deceit, he only concealed from the tyrant (as He had a perfect right to do) what He was about ultimately to effect; and in this way he detected and brought to light his obstinacy. In a word, God entered the lists for the Israelites, not in an earthly controversy, but for religion, to which all the rights of kings must give way. But Jehovah calls himself the God of the Hebrews, that Pharaoh may know him to be the peculiar God of that nation, and that their form of worship was different from the customs of Egypt, and, in fact, that he is the only true God, and all others are fictitious.

When Pharaoh refused the reasonable request of the Hebrews, God brought his people out of Egypt, out of the house of bondage, but that does not make the request to Pharaoh "deceitful." Pharaoh bore responsibility for his refusal, and in the process God's determinate will was accomplished. God was not deceitful, but kept his promises to Israel. God's attitude toware deceit is brought out in the Book of Psalms:

Psalm 24:3-5:
³Who shall ascend into the hill of the LORD? or who shall stand in his holy place?
⁴He that hath clean hands, and a pure heart; who hath not lifted up his soul unto vanity, nor sworn deceitfully.
⁵He shall receive the blessing from the LORD, and righteousness from the God of his salvation.

Psalm 72:11-14:
¹¹Yea, all kings [including Pharaohs?] shall fall down before him: all nations shall serve him.
¹²For he shall deliver the needy when he crieth; the poor also, and him that hath no helper.
¹³He shall spare the poor and needy, and shall save the souls of the needy.
¹⁴He shall redeem their soul from deceit and violence: and precious shall their blood be in his sight.

Psalm 101:6-7:
⁶Mine eyes shall be upon the faithful of the land, that they may dwell with me: he that walketh in a perfect way, he shall serve me.
⁷He that worketh deceit shall not dwell within my house: he that telleth lies shall not tarry in my sight.

Indeed, as Paul decalres in Romans:

Romans 3:4:
⁴God forbid: yea, let God be true, but every man a liar; as it is written, That thou mightest be justified in thy sayings, and mightest overcome when thou art judged.

I don't know whether this "fully" answers your question for you, but I hope that you find these comments helpful.