For it was of the LORD to harden their hearts, to meet Israel in battle in order that he might utterly destroy them, that they might receive no mercy, but that he might destroy them, just as the LORD had commanded Moses.
Calvinist, James White, comments: “God hardening hearts to destroy a people? What of their libertarian free will?” (Debating Calvinism, p.359, emphasis mine)
They exercised it, and now God is fashioning them for a useful purpose. How is this any different than with Pharaoh?
It’s the same thing as with the hardening of Israel according to Isaiah 6:10, when we find out that according to Isaiah 65:2, God had reached out to them in grace: “‘I have spread out My hands all day long to a rebellious people, who walk in the way which is not good, following their own thoughts, a people who continually provoke Me to My face, offering sacrifices in gardens and burning incense on bricks; who sit among graves and spend the night in secret places; who eat swine’s flesh, and the broth of unclean meat is in their pots. Who say, “Keep to yourself, do not come near me, for I am holier than you!” These are smoke in My nostrils, a fire that burns all the day.’”