Exodus 9:17

9:16 But indeed for this purpose I have raised you up, that I may show My power in you, and that My name may be declared in all the earth.

9:17 As yet you exalt yourself against My people in that you will not let them go.

9:18 Behold, tomorrow about this time I will cause very heavy hail to rain down, such as has not been in Egypt since its founding until now.