Question: Did God take away Pharaoh's free will when He "hardened Pharaoh's heart" (Exodus:10:1-2)? What verses point to free will in the Bible?
Response: According to Adam Clarke's commentary, the Hebrew word translated harden "literally signifies to strengthen, confirm, make bold or courageous." An illustration commonly heard is that of a sponge squeezed (made hard) in the hand. Anything that comes forth from the squeezed sponge was already there. When God "hardened" Pharaoh's heart, He simply forced out what was already there, strengthening Pharaoh's own convictions.
The Bible teaches that God elected (predestined) to save all (any) who "feareth him, and worketh righteousness" (Acts:10:34-35). According to Ephesians:2:10, one must fear God (be saved) before he can work righteousness, the works themselves being foreordained. Long before the creation of man, God predestined that men would be saved "in Christ" (Eph:1:3-4,7-12). The Lord God "predestined" His plan for the redemption of man (Eph:3:10-11).
God has also granted that man would have free will, which is simply the ability and responsibility to choose to obey Him (Gn 3:1-6; Josh:24:15; Mt 11:28; Jn:3:16). As we have noted in previous Q&As, if there were no moral response possible on man's part, then "...choose you this day whom ye will serve" (Josh:24:15) would therefore be impossible. James:4:17 instructs us that "...to him that knoweth to do good, and doeth it not, to him it is sin." This verse recognizes accountability based upon ability to do good or evil. Again, if there were no possibility of making that choice, then this verse is also meaningless.
The argument advanced by some Calvinists is that to acknowledge any measure of "ability" (i.e., "free will") in man is to leave room for boasting. The exhausted, drowning man, who hears the voice of those in the boat, cries out, "save me," and then permits the strong arms of his rescuer to pull him into the boat, has certainly done nothing to contribute to his salvation. Yet we know that some drowning men will push away their rescuers in their unreasoning panic. In each case, both are exercising choice, but neither has cause to boast. There is no room in heaven for a regenerated human heart and mind to indulge in imagined boasting for simply acknowledging one's inability to save oneself and then not interfering with the subsequent rescue.
Finally, God is certainly sovereign, but we must not deny the clear responsibility of man, regardless of our human inability to fully comprehend these differences.