And I am sure that the king of Egypt will not let you go, no, not by a mighty hand.

Wesley's Notes

3:19 I am sure he will not let you go - God sends his messengers to those whose obstinacy he foresees, that it may appear he would have them turn and live.

King James Translators' Notes

no...: or, but by strong hand

Matthew Henry's Concise Commentary

3:16-22 Moses' success with the elders of Israel would be good. God, who, by his grace, inclines the heart, and opens the ear, could say beforehand, They shall hearken to thy voice; for he would make them willing in this day of power. As to Pharaoh, Moses is here told that petitions and persuasions, and humble complaints, would not prevail with him; nor a mighty hand stretched out in signs and wonders. But those will certainly be broken by the power of God's hand, who will not bow to the power of his word. Pharaoh's people should furnish Israel with riches at their departure. In Pharaoh's tyranny and Israel's oppression, we see the miserable, abject state of sinners. However galling the yoke, they drudge on till the Lord sends redemption. With the invitations of the gospel, God sends the teaching of his Spirit. Thus are men made willing to seek and to strive for deliverance. Satan loses his power to hold them, they come forth with all they have and are, and apply all to the glory of God and the service of his church.