Pharaoh does not want to let God’s people go. The Scriptures never explicitly explain why Pharaoh was so reluctant, despite the military threat that the Egyptians feared the Hebrews could pose (see Exod. 1:10). Most likely, as is often the case with slavery, it was pure economics. They were cheap labor, and so he didn’t want to lose whatever economic advantages these slaves gave him. Thus, he was going to need some persuasion not only to get his attention but also to change his mind.