Exodus 3:18

3:18 “The elders will listen to you, and then you and the elders of Israel must go to the king of Egypt and tell him, ‘The Lord, the God of the Hebrews, has met with us. So now, let us go three days’ journey into the wilderness, so that we may sacrifice to the Lord our God.’

Exodus 4:9

4:9 And if they do not believe even these two signs or listen to you, then take some water from the Nile and pour it out on the dry ground. The water you take out of the Nile will become blood on the dry ground.”