It’s not that God overrode Pharaoh’s free will; that is, it isn’t that Pharaoh was inclined to let the Israelites go but then God stopped him from doing so. It’s that Pharaoh was not inclined to let the Israelites go, but the miracles worked by God through Moses made him timid; God gave Pharaoh the strength of will to follow through on what he really wanted to do: keep the Israelites enslaved in Egypt. In that sense, God didn’t suspend or override Pharaoh’s free will; actually, God enhanced it, so Pharaoh could make the choice that was in his heart.
This applies in other cases in which it seems that God suspends the free will of someone. In order to establish the point more clearly, it will not be superfluous to employ another illustration, as if, e.g., one were to say that it is the sun which hardens and liquefies, although liquefying and hardening are things of an opposite nature. Now it is not incorrect to say that the sun, by one and the same power of its heat, melts wax indeed, but dries up and hardens mud: not that its power operates one way upon mud, and in another way upon wax; but that the qualities of mud and wax are different. In this way, then, one and the same working upon the part of God, which was administered by Moses in signs and wonders, made manifest the hardness of Pharaoh, which he had conceived in the intensity of his wickedness but exhibited the obedience of those other Egyptians who were intermingled with the Israelites, and who are recorded to have quilted Egypt at the same time with the Hebrews.
It depends on us how we position ourselves relative to the Divine Sun.
Based on Exodus 7:3, 9:12