Exodus 9:11-12

9:11 The magicians could not stand before Moses because of the boils, for boils were on the magicians and on all the Egyptians. 9:12 But the Lord hardened ¹  Pharaoh’s heart, and he did not listen to them, just as the Lord had predicted to Moses.

[9:12]  ¹ tn This phrase translates the Hebrew word חָזַק (khazaq); see S. R. Driver, Exodus, 53.