God’s word is not simply a collection of facts. It makes moral demands on people. It condemns their unrighteousness and points them toward the all-sufficiency of Christ, whose grace in itself is also a reminder of human insufficiency. Thus, Pharaoh is both hardened by the Lord via the word, and he chooses to harden himself by not responding in faith to that which is presented to him.

Trueman, Carl R. Grace Alone—Salvation as a Gift of God: What the Reformers Taught…and Why It Still Matters (The Five Solas Series) (p. 186). Zondervan. Kindle Edition.