Assurance That Pharoah Will Not Let Israel Go

Exodus 3:16-22

16  Go, and gather the elders of Israel together, and say unto them, The LORD God of your fathers, the God of Abraham, of Isaac, and of Jacob, appeared unto me, saying, I have surely visited you, and seen that which is done to you in Egypt: 
17  And I have said, I will bring you up out of the affliction of Egypt unto the land of the Canaanites, and the Hittites, and the Amorites, and the Perizzites, and the Hivites, and the Jebusites, unto a land flowing with milk and honey. 
18  And they shall hearken to thy voice: and thou shalt come, thou and the elders of Israel, unto the king of Egypt, and ye shall say unto him, The LORD God of the Hebrews hath met with us: and now let us go, we beseech thee, three days' journey into the wilderness, that we may sacrifice to the LORD our God. 
19  And I am sure that the king of Egypt will not let you go, no, not by a mighty hand. 
20  And I will stretch out my hand, and smite Egypt with all my wonders which I will do in the midst thereof: and after that he will let you go. 
21  And I will give this people favour in the sight of the Egyptians: and it shall come to pass, that, when ye go, ye shall not go empty: 
22  But every woman shall borrow of her neighbour, and of her that sojourneth in her house, jewels of silver, and jewels of gold, and raiment: and ye shall put them upon your sons, and upon your daughters; and ye shall spoil the Egyptians.